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Medieval Doubt Loops-the-Loop, 800–1400

Muslims to Jews to Christians

It is a common assumption that doubt died in the Middle Ages: Christianity and Islam seduced and controlled everyone in a period of darkness, disease, and discomfort. We will see, instead, that doubt had some amazing adventures in this period, in a great loop around the Mediterranean Sea. This chapter will loop-the-loop of medieval rationalism. Generally, each time doubt traveled on, it was being stamped out in the last place it left. Doubt traveled mostly by coercion at first, as the Christians chased philosophy eastward and out of their territory. If we begin in Florence, Italy, a few centuries after Jesus, we find that educated people could no longer read Greek, which had been the language of books and intellectuals in Rome. A clock metaphor may help here: Florence is at twelve o’clock, and it was midnight when the mob killed Hypatia. Soon even knowledge of the existence of much philosophy would be lost in the West. At the time, doubt was more tolerated in the eastern Roman Empire, so books and intellectuals-in-exile flowed there, and were able to thrive for a while. Then this Byzantine world closed the philosophic schools in the hopes of pleasing God. This chased doubt farther east, into Syria and Persia, where there were already a few monasteries with good Greek and Roman libraries. That would be at about two o’clock, and three o’clock. Ancient rationalism, natural philosophy, and medicine survived in Syria and Persia in these tiny flickers until the Arab Muslim state rose up along the southeast of the Mediterranean and beckoned those scholars to come and teach what they knew.

The ideas continued to spread clockwise: west, across Muslim North Africa and then north into Muslim Spain. There, Jews picked up the fever of rationalism, again transforming it, and the Christians took it up and spread it back through Europe. A great wealth of material was back in Florence by the year 1200 (it’s a nice coincidence with my clock metaphor, which is about geography). Much of the ancient material had been fitted for monotheism by then. This mix of faith and philosophy had created wonderfully bizarre new kinds of doubt. So let us begin our loop-the-loop.

It is funny that Greek philosophy was first taken to Asia with Christians, but it was. Saint Ephrem founded a Christian school at Edessa, in Mesopotamia, in 363. Its faculty had studied philosophy in Athens and, along with their theology, they taught Aristotle’s philosophy and the medical writings of Hippocrates and Galen. Many Nestorian scholars who went east after the condemnation against Nestorianism in 431 ended up at the school of Edessa. Indeed, the school grew too Nestorian for the emperor Zeno’s taste and he ordered it closed in 489. The Nestorian professors who were chased away went to Persia and took with them Syriac translations of some of Aristotle’s works; they translated these and others into Persian. Back in Syria, the school of Edessa became a new Monophysite school. Monophysites propagated the view that Jesus was not really human but only divine—of one nature, not two as orthodox Christianity held—but they continued the Nestorians’ habit of studying Aristotle and also continued the work of translating Greek texts into Syriac. So by the time Justinian and Theodora shut down the Byzantine philosophical schools in 529 (at one A.M. on our clock of the Mediterranean), there were already places for the displaced philosophers to go, farther east (at two o’clock), where Nestorians had prepared the way. The scholars were welcomed into Persia in their exile. There, in these few sites, the great heritage of doubt in the Western world smoldered quietly. But not for long.


While the West was in its darkest days, a new faith arose in the East. Muhammad of Mecca lived from 570 to 632 and in his own lifetime saw the beginning of a great expansion of the religion he inaugurated. Within a hundred years, the Islamic world had expanded, by military conquest, from India, through North Africa, and into Spain. Islam was envisioned as a continuation of Judaism and Christianity, and Muhammad saw Moses, Jesus, and himself as the great prophets of a single God. The big difference was supposed to be location (this time the message was being brought to the Arab world) but, by and large, the Jews and Christians were not amused by the “corrections” of their faith. The Koran supposes that on Judgment Day, God will ask Jesus, “Didst thou say unto men: worship me and my mother as gods in derogation of God?” and assures its readers that Jesus will deny having done so.1 This certainly riled up the Christians, but we see nothing new in such debate over religious detail. Muhammad’s religious vision was, of course, a radical questioning and rejection of the tribal paganisms of Arabia. If anything was new in the history of doubt, here at the birth of Islam, it was in the clarity of the command to surrender to belief in God. Indeed, Islam and Muslim are variations on the same Arabic word, whose meaning is to submit. The masses may have done so, but the intellectuals of the Muslim world had access to more ancient texts than did the intellectuals of Byzantium or the west—and that made all the difference.

There were three main sects of the Muslim world. The largest were the ahl al-hadith, the Traditionalists. Their ideas appealed to ordinary people, in part because they believed that every person had the ability to know God, through the Koran. Priests were unnecessary and each individual had to be treated with respect. The Shia branched off in their dedication to descendants of Muhammad’s daughter, Fatima, and her husband, Ali, who was Muhammad’s cousin. The Shia were very concerned with succession obviously, and it was a crisis for them when the childless, twelfth-descended Imam went into hiding in 939 and was never heard from again. In response, the Shiites developed a notion that he had experienced some kind of apotheosis: the twelfth, Hidden Imam would eventually return and begin a great new Muslim golden age. In their origins, Shiites were often more interested in rational explanations of God than their mainstream coreligionists were. The third sect, the Mutazilis, were more rational still, welcoming philosophical speculation and logical proofs, and comfortable using allegory to explain away the anthropomorphism of the God of the Koran: God’s “hands,” for example, referred to his generosity and benevolence.

The differences that the Traditionalists, the Shiites, and the Mutazilis had with each other were about economic, political, and social issues as well, but these are outside our present concerns. What we need to know here is that the Mutazilis came to believe that the essence of God was justice. They liked the idea for its own internal logic but also because it preserved human free will: God could do no injustice or sin, so if there is so much injustice and sin on earth, it proves that we have the ability to make our own decisions. This gives us responsibility and demands that we attend to theories of ethics. The Traditionalists attacked the Mutazilis for making God too rationalist and embraced the idea of predestination as a response: God’s justice was incomprehensible, it was all in his hands, all else was hubris. Justice itself, they argued, was a purely human ideal, and we must not assume that God is beholden to it.

Some Traditionalists claimed that the Mutazilis had removed all religious value from their philosophical concept of God. Traditionalists eventually declared that no rational discussion of God should be permitted. To many, this seemed extreme. A compromise was struck when Abu al-Hasan ibn Ismail al-Ashari (878–941), a Mutazili, dreamed that Muhammad instructed him to turn to the Traditionalist studies. Later, after earnestly condemning Mutazilis, al-Ashari had another dream of the Prophet and was this time instructed not to be such a fanatic about it. A peeved Muhammad, he tells us, appeared and said, “I did not tell you to give up rational arguments, but to support the true hadiths!” The upshot was that al-Ashari founded the Muslim tradition of Kalam, literally theology, which was based on logic but did not hold God to that logic. The idea was that Muslims ought to use reason and logic to show that God was beyond human understanding. So there had been Muslim rationalism in the Mutazili sect, and it had influenced a new, more rationalist mainstream. Yet, at the same time, among the early Muslims there were a few deeply independent scholars who doubted almost all the features of God that made him godlike, i.e., that God was good, that he made the universe, or that he cared about humanity. They were often referred to as atheists. There are two major figures here: the amazing Ibn al-Rawandi and the equally surprising al-Razi. But first we must attend to the rise of Falsafah, the dynamic philosophical movement that appears in the Muslim world as a sudden flood of Greek texts becomes available.

One of the reasons the Islamic world spread so far, so fast, was that the two giant empires it demolished—Byzantium and Persia—had just exhausted themselves fighting each other in a series of wars. Also, these old empires were very diverse, so the Muslims took them on in small bursts, in piecemeal fashion. What’s more, the considerable population of heretical Christians happily yielded to the Muslims because, while the dominant Christians sometimes forced the heretics to convert or die, the Muslims merely demanded taxes, not conversion, from other “people of the book”—Jews and Christians. All this conquering meant that in these centuries Muslims were constantly confronted with Judaism, Christianity, Indian religion and philosophy, Manichaeism, Zoroastrianism, and some Greek and Roman ideas. It was this wildly heterogeneous world that was taken over in the Abbasid Revolution, a momentous political uprising in 750. The Abbasid dynasty reigned until the thirteenth century and brought the Muslim world its first golden age. When the Abbasids established their residence in Baghdad, Syrian scholars and doctors—many of whom were Nestorian and Jacobite (Syrian Monophysite) Christians—were invited to live, teach, and work there. When the Syrian scholars came to Baghdad, they brought their texts. Their medical treatises were the first to be translated into Arabic, but soon the focus shifted away from things of pragmatic, immediate use and toward philosophy itself.

Over the course of the ninth century the Arab world began a spectacular program of translation. There was a hunger for the ancient discussion of many areas of intellectual life. The Nestorian Christians, who spoke Greek and Arabic, first translated the books they had. Then they went in search of ancient texts preserved in the dark recesses of the libraries and monasteries of the Eastern Church, and in the monasteries that were outposts of Christianity in the Muslim world. Soon enough, there were Arabic translations of Euclid, Archimedes, Ptolemy, Hippocrates, Galen, all of Aristotle except the Dialogues and the Politics, Plato’s Timaeus, Republic, and Laws, as well as the works of a few lesser-known figures. There was also something called The Theology of Aristotle, which was actually excerpts from Plotinus’s Enneads! That this seemed reasonable reminds us of the degree to which Neoplatonism had been mixed into everyone’s idea of Aristotle. These “new” texts were translated from the Greek directly into Arabic or, often enough, into Syriac and then into Arabic. There were some stars in this effort. A father-and-son team in the ninth century—a Nestorian court doctor named Hunayn ibn Ishaq and his son Ishaq—made more works of Galen, Euclid, and Ptolemy available in Arabic than were ever available in Greek-speaking Byzantium. The father translated the books from Greek to Syriac, and then the son translated them from Syriac to Arabic. Working with these ancient texts, the Arab world made more scientific discoveries than had been made at any previous period in history.

There also arose a philosophical humanism that celebrated the scientific and philosophical heritage of classical antiquity as a cultural and educational ideal.2 Individualism and literary humanism was cultivated in the arts and politics. This golden age thrived in a Baghdad that had become a remarkably cosmopolitan place in terms of its arts and the urbanity of its citizenry. It was the center of both the Abbasid Empire and, after 945, of Buyid rule. It was in this context that the Faylasufs emerged, lauding Greek philosophy and adopting it as their own, with some Muslim adjustments. Their movement, Falsafah, held that the God of the Greek philosophers was identical to Allah. The Faylasufs came to believe that God was reason itself.

Yaqub ibn Ishaq al-Kindi (died ca. 870) was the first to approach the Koran through Greek philosophy, the first of the great Muslim Aristotelians. It was daring of him to do so, but he justified the act by using the old notion of philosophy as the handmaid of revelation. In a way this was made easier by a terrific interpretive error: the Arabic-speaking world in this period thought that Aristotle and Plato were the same person and were at work reconciling the contradictions in this genius’s work. Plotinus’s combination of the religious suggestions of Aristotle and Plato fed the error. Al-Kindi wrote that Muslims “should not be ashamed to acknowledge truth and to assimilate it from whatever source it comes to us, even if it is brought to us by former generations and foreign peoples.”3 Al-Kindi used Aristotle’s proof of the necessity of a prime mover, but differed with Aristotle (and favored the Koran) in his assertion that the universe was created out of nothing. After al-Kindi, Falsafah seems to have always sided with Aristotle on this matter, despite its direct contradiction of the Koran. In general, the Faylasufs based their own knowledge in reason and disagreed with the Koran without much fanfare. They maintained that the Koran was a valid path to God for those who were incapable of finding their way to truth through reason—but for anyone who could follow the path of reason, well, that was more exquisitely true.

The rise of skepticism among Muslims grew out of the problem of prophecy. Prophecy had a central place in Islam. By the time Islam came along, the Jews had been finished with prophets and prophecy for about eight hundred years. Having broken with Judaism, the Christians were in a more imminent and malleable religious tradition; that is, they believed that new and earthshaking religious information was still being offered by God. That made them more open to prophetic types of speech than were the Jews, but they, too, did not admit contemporary prophets; everyone knew that the prophetic age was over centuries ago.

Before the rise of Islam, Jews and Christians did not have much of a literature on how to recognize a true prophet. There was a discussion of it in Deuteronomy, which suggested that a prophet should be attended by miracles, but that was about it. By the ninth century, however, Jews, Christians, and Muslims had each created a body of literature on the topic. As Sarah Stroumsa explains in her Freethinkers of Medieval Islam, it seems to have begun with Muslims defending themselves against the angry disbelief of the Jews and Christians, followed soon after by a response from those Jews and Christians.4 The earliest of this Islamic work has been lost to time, so the prophetology we find in the ninth century was already a mature body of thought. One of the earliest important surviving works is Proofs of Prophecy by Jahiz, which gives much attention to the idea that the Koran was so beautiful that it was the miracle that validated Muhammad’s word. He also argued that the Koran showed knowledge—knowledge of the history of the Jews, for example—that Muhammad could not have known by natural means. The Christians and the Jews argued against it, of course, but many of these believers ended up defending prophetology against deeper doubt.

Much of this was written in the form of dialog or argument. The role of the disbeliever was generally cast as either the Greek philosophers or, more marvelously, Barahima, the Brahmans, whom Muslims saw, essentially, as antiprophetic rationalists.5 After a while, sometimes the doubter won.

The term zindiq started out meaning “secret dualist”: calling someone a zindiq meant you suspected him of harboring Manichaean sympathies beneath his public Islamic piety. Manichaeism had been “Hellenized” in the four centuries since Augustine professed it; its intellectuals rationalized the belief system and read the ornate cosmology as allegory. The heresy (zandaqa) of Manichaeism was the way of a Muslim with a taste for rationalism. As the period of great Muslim doubters got going, zindiq started to mean religious doubters and zandaqa started to mean religious doubt. The first person to be executed for zandaqa was Djad ibn Dirham, in 742. He is said to have denied the Muslim concept of a God with attributes, saying, “God did not speak to Moses, nor take Abraham as his friend”; he was also known as a materialist. He had a following who were reputed to believe that Muhammad had lied and who denied the resurrection. Ibn al-Muqaffa was executed in 760 for Manichaeanism and for attacking Islam, its prophet, and its notion of God.

The poet Abu Nuwas was a famous doubter of that time. At his mosque one day, when the imam began to read out verse one of sura 109, “Say: O! You unbelievers…,” Abu Nuwas is said to have yelled out, “Here I am!” When the police hauled him to the inquisitor, a portrait of Mani was produced and Abu Nuwas was told to spit on it. They clearly had the old idea of zandaqa in mind. Abu Nuwas demonstrated the extent of his doubt, answering their challenge by sticking his finger down his throat and vomiting on the picture of Mani. The zindiq Inb Abi-l-awja was executed in 772 for believing in the eternity of the world and denying the existence of a creator. He also had a problem with providence, asking, “Why are there catastrophes, epidemics, if God is good?”

A whole circle of zindiq poets existed in these years. The historian Ignaz Goldziher gives us this picture: “It is reported that at Basra a group of freethinkers, Muslim and non-Muslim heretics, used to congregate and that Bashshar ibn Burd did not forego characterizing the poems submitted to this assembly in these words: ‘Your poem is better than this or the other verse of the Koran, this line again is better than some other verse of the Koran, etc.’” The doubters also specifically critiqued the Koran. For instance: “Al-Mubarrad tells of a heretic who ridiculed the parable in sura XXXVII.63, where the fruits of the tree Zakkum in hell are likened to the heads of devils. The critics say: ‘He compares the visible with the unknown here. We have never seen the heads of devils; what kind of simile is this?’”6

Abu Nuwas relates a comment made by Aban, one of the freethinkers of Basra. It happened just after the call to prayer one day. “Then said Aban: How could you testify to [Muslim belief] without ocular demonstration? So long as I live I shall never attest anything but what I see with my eyes.’” At the mention of God having spoken with Moses, Aban supposedly said, “Then your God must have a tongue and an eye. And did He create Himself, or who created Him?”7

We come now to the two major authors of Muslim doubt: Ibn al-Rawandi and Abu Bakr al-Razi. We do not know much about Ibn al-Rawandi. Some scholars think he died about 860 and others that he lived until 912 or so. Some have seen him simply as an Aristotelian philosopher and others as a radical atheist. He is not generally understood within the Falsafah tradition, which was just getting under way in his era: he started out as a Mutazili but came to reject his colleagues and then to extend his critique, rejecting ever more fundamental notions of Islam, of revealed religion, and of theism itself. He wrote many mainstream scholarly works and an amazing amount of heretical work. In bold agreement with Aristotle, he supported the eternity of the world, though it meant that God did not create it. This point, which was a relatively small one in Aristotle’s work, would become a major part of how everyone thought of him in the Middle Ages—and a real sticking point for all three great monotheist traditions. Al-Rawandi started it. He also took on such positions as: “against the idea that God is wise,” “against the Koran,” “against Muhammad,” and “against all prophets”!

Ibn al-Rawandi’s most important book was the very curious Kitab al-Zumurrud, or The Book of the Emerald. It survives only in detailed descriptions and some quotes in other texts. The book was a conversation between the author and his friend and mentor, the scholar Muhammad al-Warraq. In the beginning of The Book of the Emerald, it is the friend who is the most radical, but soon al-Rawandi’s doubt goes further than al-Warraq’s.

Al-Warraq was Muslim, but Muslim sources call him a Manichaean. He was certainly a doubter. Al-Warraq often referred to God as an idiot, because “He who orders his slave to do things that he knows him to be incapable of doing, then punishes him, is a fool.”8 The provocative and sarcastic role he played was purposefully disruptive, and he did not seem to mind being held in general disrepute, even courting it. Details of al-Warraq’s life are vague, but we know that after a while he was persecuted, and after his death his books were banned and destroyed. We know him mostly through the excerpts found in polemics against him.

In The Book of the Emerald, al-Warraq explains the problems of prophecy, while his student Ibn al-Rawandi tries to defend it. Al-Rawandi insists, for instance, that Moses and Jesus both predicted the coming of Muhammad. Here’s what he has the al-Warraq character say:

Moses and Jesus did indeed predict the coming of Muhammad; any astrologer can make correct predictions. In the same way, the fact that Muhammad could predict certain events does not prove that he was a prophet: he may have been able to guess successfully, but this does not mean that he had real knowledge of the future. And certainly the fact that he was able to recount events from the past does not prove that he was a prophet [because he could have read about those events in the Bible] and, if he was illiterate, he could still have had the Bible read to him.9

Al-Warraq also argued, this time citing a Brahman, that if the prophets’ claims support human judgment—if we are capable of figuring out, say, that it is good to be forgiving—then the prophets’ claims are unnecessary. If these claims are contrary to what God’s gift of intelligence reports, then we should not listen to them. This rips the rug out from under the entire notion of revealed religion. It did not praise the intellect for its capacity to know God but for the wonder of science. Al-Warraq explained that people developed the science of astronomy by gazing at the sky, and no prophet was necessary to show them how to gaze. No prophets were needed to show them how to make lutes, either, or how to play them. Humanity learned by itself that if you remove the intestines of a sheep, dry them, and stretch them over a piece of wood, it can make pleasing sounds when pounded upon. According to Ibn al-Rawandi, we figured all this out through natural intellect, study, observation, and trial and error. We can know the world on our own.

With a stubborn reliance on material explanations and human ability, Ibn al-Rawandi suggests that maybe the Koran is more beautiful than other Arab books because Muhammad was an extraordinary composer of words, or because the other Arabs were too busy fighting off Muhammad to take time to write poetry, or because the Arabs were an uneducated people. He then offers the opinion that the Koran is not that beautiful anyway. The book, he asserts, says contradictory and absurd things and is not particularly impressive to non-Muslims. The Book of the Emerald even points out that Muhammad’s teachings themselves represent a challenge to revealed religion: he had claimed that all sorts of things that Jews and Christians believed were entirely wrong, that those things had been passed down from their prophets incorrectly. But, wonders Ibn al-Rawandi, if you cannot trust the great multitude of Jews and Christians to get the facts right, why should one trust the handful of Muhammad’s followers who passed down the Muslim tradition?10

There were events in Muhammad’s life that were explained in the Koran as having been determined by the military help of angels. Ibn al-Rawandi wrote that this helps explain why Muhammad did better than one might have expected at Badr, but it begs the question of where these angels were at Uhud, and indeed, why even at Badr they killed only seventy of Muhammad’s enemies. The angels should have been able to do better. The Book of the Emerald actually assigns a kind of cheating to the prophets. They were not deluded or mistaken; they were actively faking, using tricks and sleight of hand to fool their audience. In a delightful praise of rationalism, the book argues that the prophets used weird and little-known natural phenomena—like magnets but less famous—to defraud their followers. The Book of the Emerald also criticizes prayer, concern for ritual purity, and all the ceremonies of the hajj: walking around a great stone, it claims, cannot really help anyone. It even asks why the Ka’ba “is better than any other house.” Ibn bows to his friend’s ideas at the end of the book.

Soon al-Rawandi’s doubt was thoroughgoing. He was known to systematically write books and then to write their refutation. He is also said to have “composed for the Jews the Al-Basira, refuting Islam, for the sum of 400 dirhams, which as I have heard, he received from the Jews of Samarra. Having collected the money, he contemplated writing a refutation of it, until they gave him an additional hundred dirhams, for which he abstained from writing the refutation.”11 We do not know if he was directly influenced by the Skeptic tradition, but his was a new voice in its canon. Among his other books, Ibn al-Rawandi wrote Against the Koran and a little treatise called The Futility of Divine Wisdom. In their content and tone, these books seem to mark a complete break with Islam. He mocks the philosopher’s idea of God as “universal force” that does not know how to add two and four to get six; he concludes that if the world’s events are the result of willful action, then God must be a wrathful, murderous enemy.

The writer al-Hayyat, who died about 913 CE, had this to say about Ibn al-Rawandi: “He disputed the reality of the miracles of Abraham, Moses, Jesus and Muhammad and claimed that they were fraudulent tricks and that the people who performed them were magicians and liars; that the Qur’an is the speech of an unwise being, and that it contains contradictions, errors and absurdities.”12 Further, he said that, according to Ibn al-Rawandi, a God who inflicts illness upon his slaves cannot be counted as one who treats them wisely, “nor can he be said to be looking after them or to be compassionate toward them. The same is true concerning he who inflicts upon them poverty and misery. Also unwise is he who demands obedience from a person who he knows will disobey him. And He who punishes the infidel and disobedient in eternal fire is a fool.”13 Al-Rawandi grew contemptuous of those who reconciled innocent human suffering with a caring, benevolent God, and that contempt got him into trouble. He was so hated that by the eleventh century it was difficult to find any of his manuscripts. Yet this vibrant and inventive voice in the history of doubt was never quite forgotten.

We cannot say that Ibn al-Rawandi was Falsafah, for they did not claim him, nor he them. He was just a little further into apostate than internal critique. Yet there was a man who was as radical in his doubt but who was tolerated by the establishment and able to help create and animate the rationalist Islamic movement: Abu Bakr al-Razi, the other star of early Islamic doubt. Before we look at him directly, let us listen to what people have said of him: al-Razi has been called “the greatest nonconformist in the whole history of Islam,” “the most free-thinking of the major philosophers of Islam,” “the least orthodox and the most iconoclast,” “perhaps the single figure most frequently denounced and disapproved as a heretic in the subsequent history of Islamic thought,” and in the words of a recent study of his work, “If, however, the sayings attributed to him are authentic, his doctrine emerges as irreconcilable with any kind of Islam, however open-minded.”14 Yet al-Razi was beloved.

The reason one was hated and the other cherished was simple: where Ibn al-Rawandi was provocative, sarcastic, and happy to play the role of the outsider, correcting the gullibility of the majority, al-Razi was a doubter who devoted himself to his community’s well-being and grew famous for his generosity, intelligence, and skill. He was a doctor and has been called the most creative genius of medieval medicine. He has also been lauded as both a philosopher and a chemist and he served as the director of hospitals in his native Rayy, Iran, and at Baghdad. Al-Razi’s books became classical works on Arabic medicine, and a few were well known in the West; his study of pathology and therapy was translated into Latin and long served as a teaching manual in various universities in Europe. He was often called “the Arab Galen,” a name he earned not through sycophantic repetition of Galen’s doctrines but by representing Galen’s dedication to experimentation and observation.

Al-Razi’s dates are usually given as 854–925, which means he flourished at the same time that Islamic thought was reaching maturity in various arenas: it was the zenith of Mutazilism; the first phase of the translation movement was being completed; and Islamic interest in Neoplatonism was at its peak. The period also saw the crystallization of Falsafah, as al-Razi is often considered the first true Faylasuf. The names of three of his books were The Prophet’s Fraudulent Tricks, The Stratagems of Those Who Claim to Be Prophets, and On the Refutation of Revealed Religions. In them, al-Razi asked groundbreaking questions about prophets: “On what ground do you deem it necessary that God should single out certain individuals” by giving them prophecy, “that he should set them up above other people, that he should appoint them to be the people’s guides, and make people dependent upon them?”15 How could it be possible that a God would choose this method, since it invariably incites people against one another, spreads hostility, and increases fighting? The “most fitting” behavior of the Wise One would be to give everyone the same necessary knowledge. “He should not set some individuals over others, and there should be between them neither rivalry nor disagreement which would bring them to perdition.”16 It is a rotten situation, and no planning, compassionate God would invent it.

With such a variety of religions, al-Razi said, anyone could have foreseen that “There would be a universal disaster and they would perish in the mutual hostilities and fightings. Indeed, many people have perished in this way, as we can see.” Al-Razi also wrote, “If the people of this religion are asked about the proof for the soundness of their religion, they flare up, get angry and spill the blood of whoever confronts them with this question. They forbid rational speculation, and strive to kill their adversaries. This is why truth became thoroughly silenced and concealed.”17Here and elsewhere, his language is festooned with references to proof, soundness, questions, and rational speculation. He saw religious people as having been originally duped by authority figures and explained that they now continued to conceal the truth

as a result of their being long accustomed to their religious denomination, as days passed and it became a habit. Because they were deluded by the beards of the goats, who sit in ranks in their councils, straining their throats in recounting lies, senseless myths and “so-and-so told us in the name of so-and-so…”18

This passage alone has been described as “the most violent polemic against religion in the course of the middle ages.”19 It may well have been, as it has a sharp blade with its smiling “so-and-so’s.” Al-Razi was able to get away with this ruthless religious critique because he did so much more: most people who wrote about him concentrated on his impressive body of scientific work and simply left his strange, extreme antireligious arguments to the side.

Al-Razi thought the variety of religions was a good proof that none of them had it right: “Jesus claimed that he is the son of God, while Moses claimed that He had no son, and Muhammad claimed that he [Jesus] was created like the rest of humanity.” What is more, “Mani and Zoroaster contradicted Moses, Jesus and Muhammad regarding the Eternal One, the coming into being of the world, and the reasons for the [existence] of good and evil.”20 He picked apart the Christian claims about Jesus and mocked the Torah’s imagining of God as an angry old man, “white-haired and white-bearded.”21 Not only that, the Hebrew God frequently asked for sacrifices of particular quality and quantity. “This sounds like the words of the needy rather than of the Laudable Self-sufficient One.”

Abu Bakr al-Razi claimed that the supposed miracles of prophets were not good evidence of their validity. For one thing, “similar feats were performed by people who made no claim of prophethood,” and he mentioned all sorts of feats by wonderful but purely human tricksters, from juggling and legerdemain, to dancing on spikes and walking on spears, to the rhyming speech of oracles and soothsayers. As for the Koran, it is best to hear the diatribe in al-Razi’s own words:

You claim that the evidentiary miracle is present and available, namely, the Koran. You say: “Whoever denies it, let him produce a similar one.” Indeed, we shall produce a thousand similar, from the works of rhetoricians, eloquent speakers and valiant poets, which are more appropriately phrased and state the issues more succinctly. They convey the meaning better and their rhymed prose is in better meter.… By God what you say astonishes us! You are talking about a work which recounts ancient myths, and which at the same time is full of contradictions and does not contain any useful information or explanation. Then you say: “Produce something like it?!”22

Al-Razi wasn’t really against ancient myths; he liked them, but he did not think the Koran qualified as a true mythology. A true mythology, he held, ought to read like a riddle, an allegory whose contemplation would lead to higher philosophical speculation, and in his view the Koran did not. He was not just trying to correct religion, though. Al-Razi made it clear that he thought all supposedly revealed religions were a disaster for humanity, because they led to bloodshed and because religious authorities tended to be cruel and despotic.

For al-Razi, human beings could negotiate existence on its most profound level without religion. How? “No soul can be purged from the turbidity of this world and escape to the next, except by contemplating philosophy. If a person contemplates philosophy and comprehends anything, be it ever so small, his soul is purged from this turbidity and is saved.”23 Advice like his could not be meant for oneself alone. Al-Razi knew a cosmopolitan doubting world and was offering comfort to its members. He was treated as a hero by them long after his death.

The Faylasufs in general were rationalists, and they belong to the history of doubt, but compared to al-Razi most were pretty tame. In fact, they came to accept prophetology: the intellect was understood as extraordinarily powerful, but for most people it was never going to be enough, and that’s why the prophets were needed. The Faylasufs were accused of writing “as if” they were denying prophecy, and it was often said that their doctrine “amounted to” being against prophecy, but whereas al-Rawandi and al-Razi both denied the fundamental tenets of Islam, the Faylasufs found ways to support many of them. We should note that these were cosmopolitan, rationalist times and religious communities shared the mood. The Ismailis and their subsect “The Brethren” dedicated themselves to science and mathematics in order to discover the hidden meaning of life. The Brethren wrote that in search of the truth, we must “shun no science, scorn no book, nor cling fanatically to a single creed.”24 They were deeply influenced by Neoplatonic texts, even rejecting the Koran’s claim of ex nihilo creation in favor of the Platonic idea of emanation. As I have mentioned, the Faylasufs also disagreed with the Koran on this issue, in favor of Aristotle’s eternity. There was a lot of room for doubt.

The greatest of the Faylasufs was Abu Ali ibn Sina, known in the West as Avicenna (980–1037). Like Abu Bakr al-Razi, Avicenna was a famed medical doctor. He was born into a Shii family and was later attracted to Falsafah. After he cured the sultan of Bukhara, the sultan hired him and gave him access to a considerable library. He attributed his Neoplatonist understanding of the world to the reading this allowed him. Arguably, before Avicenna, Falsafah was an Aristotelian philosophical movement that took place within the Muslim world but was not really a Muslim movement, not a movement within the religion. Avicenna saw that Falsafah seemed elitist to people but believed it could save them from the mundane world, from fear of death, and from confusion, if only they could understand it. But even if the people could understand it, it was not human enough for them: there was no way to pray for things or talk to God or other spiritual beings, no face to imagine or arms to lean on, and there was no afterlife. Avicenna understood Aristotle in terms of the Neoplatonist idea of emanation—divine thought emanating the world into being—and declared that, in this sense, it was philosophically sound to speak in terms of a created world. It was not exactly the way it was presented in the Koran, but to some at least, it seemed closer.

This emanation idea allowed for a philosophical God who was not a personality but who was in the world and in some vague sense knew the world, since, after all, the world was an emanation of him. One could thus commune with this God in a way that was impossible if God were Aristotle’s prime mover. In fact, the idea continued, sometimes this emanation is sufficiently powerful to allow for prophetic speech. But that did not quite mean this would be speech that was literally true. Thus Muhammad’s abilities as a prophet allowed him to speak real truth in human terms, so that the average person could understand it. Just as important, Avicenna found a way to speak of an afterlife that also came from a Neoplatonic reading of Aristotle.

As far as he was concerned, anyone who was capable of philosophy was called to do it, and would want to—it was a moral responsibility to seek truth, but it was also the best game in town. God was understandable intellectually, and that was the sweetest and highest way. Intellectuals thus had access to some of the joys of revealed religion without entirely contradicting their rationalism, and mystics could support their otherwise antirationalist experiences with philosophical argument. Falsafah reigned for a couple of centuries in an efflorescence of arts and letters, learning and science, commerce and cosmopolitanism.

Islamic literary tradition often says that the three worst zindiqs of Islam were al-Rawandi, al-Tauhidi, and al-Ma’arri. We have met al-Rawandi, the philosopher; the other two were poets. Al-Tauhidi left us few overtly heretical ideas; he may have written more incendiary things that have been lost, or perhaps his interest in Greek philosophy and science was passionate enough to seem like zandaqa on its own. As for Abdallah al-Ma’arri (973–1057), he was alive at the end of the movement and was a fabulous character in the history of doubt. He was born in Syria, contracted smallpox as a child, and eventually went blind from it. We should meet him through his verse:

By fearing whom I trust I find my way

To truth; by trusting wholly I betray

The trust of wisdom; better far is doubt

Which brings the false into the light of day

Al-Ma’arri specifically lauded doubt. His criticisms also echoed Xenophane’s theme that people believe what they are brought up to believe: “Our young man grows up in the belief to which his father has accustomed him. / It is not Reason that makes him religious, but he is taught religion by his next of kin.”26

They recite their sacred books, although the fact informs me that these are a fiction from first to last.

O Reason, thou (alone) speakest the truth. Then perish the fools who forged the religious traditions or interpreted them!27

O fools, awake! The rites ye sacred hold

Are but a cheat contrived by men of old

Who lusted after wealth and gained their lust

And died in baseness—and their law is dust.

What did he advise then? “Devout is he alone who, when he may / Feast his desires, is found / With courage to abstain.”29 Al-Ma’arri also enjoyed reminding his readers that the sacred stones in Mecca, “visited and touched with hands and lips,” in actuality “are stones that once were kicked.”30 He was also interested in the cosmopolitan argument: “They all err—Moslems, Christians, Jews, and Magians”—because there are only two types of “Humanity’s universal sect”: “One man intelligent without religion / And one religious without intellect.”31 What’s more: “The Christian, as more anciently the Jew / Told thee traditions far from proven true.”

The Christians have lied concerning the Son of Mary

The Jews also lied concerning the Son of Amran.

And never the Days have brought forth new in nature,

Nor ever did Time depart from his ways accustomed

Religion and infidelity, and stories that are related, and a Revelation that is cited as authority, and a Pentateuch and a Gospel.

Lies are believed amongst every race; and was any race ever the sole possessor of Truth?33

He wrote that “If a man of sound judgment appeals to his intelligence, he will hold cheap the various creeds and despise them,”34 and thought only physical punishment could have ever made human ancestors accept religion in the first place:

Had they been left alone with Reason, they would not have accepted

a spoken lie; but the whips were raised (to strike them)

Traditions were brought to them, and they were bidden say,

“We have been told the truth”; and if they refused, the sword was drenched (in their blood).35

The period of Falsafah, which supported such doubt, did not last forever. It broke down at the end of the eleventh century, in part because of the actual psychological breakdown of one of its followers, Abu Hamid al-Ghazzali.

Al-Ghazzali (1058–1111) pushed Falsafah so far that he became not only a doubter in the rationalist tradition but also a doubter in the tradition of the dark night of the soul. When he arose from that dark night, it was not to bathe in the light of the intellect but to seek and cultivate a light from within. At thirty-three, al-Ghazzali was the director of a prestigious mosque in Baghdad, but he did not have a settled mind. He wanted to know God for certain, writing that he had “poked into every dark recess… made an assault on every problem… plunged into every abyss… scrutinized the creed of every sect” in his effort to know the truth.36 He wrote a book, The Opinions of the Philosophers, that respectfully and accurately described Aristotle’s thoughts on God as derived by Avicenna and others. He later wrote a book called The Incoherence of the Philosophers. In it he stated that he’d found twenty propositions of Aristotle that were not sufficiently demonstrated, and he spent most of his energy on these philosophical problems. But he also noted that the God of Falsafah, the God that seemed to him to be the God demonstrated by Aristotle and Plato, was not very Islamic and was not very helpful. With no bodily resurrection and with a God that does not really know individuals, there was not much hope here of a religious nature. Not only that, but he thought the emanation idea was actually another way of thinking that the world was eternal, even if the Faylasufs denied it.

This rejection of philosophy was joined by a rejection of all other conceptions of truth that he had encountered. In one historian’s words, “Al-Ghazzali was as aware as any modern skeptic that certainty was a psychological condition that was not necessarily objectively true.”37 He spokepassionately against the Muslims who claimed to know God through present or hidden imams; and against the Sufis, who believed they knew God through their mystical practices; and Falsafah, who claimed to know God through their intellects—for how did any of them know that their imams, or visions, or proofs were really true? He could not stop struggling for certainty, and in or about the year 1094 he came to a crisis. His breakdown had physical dimensions: he could not swallow or move his tongue. In his Deliverance from Error, he recorded that he had been brought to the edge of Skepticism because of the failures of the proofs of God.

When he was an adolescent, he explained, he noticed “that Christian youths always grew up to be Christians, Jewish youths to be Jews and Muslim youths to be Muslims.”38 So what was belief? He set out to find the truth through study and concluded that the knowledge he had been given in his youth was not sufficiently grounded. Thus he found himself relying on nothing but sense perception and what seem to be “necessary truths”; but soon “Doubt began to spread here and say: ‘From where does this reliance on sense-perception come?’” A shadow looks to our eyes like it never moves, yet it moves, and not all that slowly. The sun looks like it’s the size of a coin, “yet geometrical computations show that it is greater than the earth in size.”39 He also asked, given the fact of dreams, “Why then are you confident that all your waking beliefs, whether from sense or intellect, are genuine? They are true in respect of your present state; but it is possible that a state will come upon you whose relation to your waking consciousness is analogous to the relation of the latter to dreaming. In comparison with this state your waking consciousness would be like dreaming!” Al-Ghazzali proclaimed that “the disease was baffling” and lasted almost two months, “during which I was a sceptic.”40

He then came to describe philosophy as having four camps: the ones who “derive truth from the infallible imam”; the philosophers; the scholarly theologians; and mystics such as the Sufis.

I said within myself: “The truth cannot lie outside these four classes. These are the people who treated the paths of the quest for truth. If the truth is not with them, no point remains in trying to apprehend the truth. There is certainly no point in trying to return to the level of the naïve and derivative belief once it has been left, since a condition of being at such a level is that one should not know one is there; when a man comes to know that, the glass of his naïve beliefs is broken. This is a breakage which cannot be mended, a breakage not to be repaired by patching or by assembling of fragments.”41

His assumption that the choices supplied by his historical moment were the only important ones is instructive. The second thought was more impressive: no one had ever recorded the psychology of doubt like this, recognizing a level of belief as necessarily unnoticed by its proponent.

Al-Ghazzali came to believe that all the various philosophers were affected by the “defect of unbelief,” especially the materialists.42 He offered this description of them as people who think the world has been eternally here “of itself and without a creator, and that everlastingly animals have come from seed and seed from animals; thus it was and thus it ever will be.”43 It was intended to dismiss the naturalists in his midst but acts as a lovely testament to their existence. Al-Ghazzali liked Aristotle best of all philosophers, “yet he too retained a residue of their unbelief… we must therefore reckon as unbelievers both these philosophers themselves and their followers among the Islamic philosophers, such as Avicenna.” What must we read then? Well, we must read carefully. Even math can be dangerous, and again his warning gives witness to the state of doubt around him:

Every student of mathematics admires its precision and the clarity of its demonstration. This leads him to believe in the philosophers and to think that all their sciences resemble this one in clarity and demonstrative cogency. Further, he has already heard the accounts on everyone’s lips of their unbelief, their denial of God’s attributes, and their contempt for revealed truth; he becomes an unbeliever merely by accepting them as authorities, and says to himself, “If religion were true, it would not have escaped the notice of these men since they are so precise in this science.” Thus … he draws the conclusion that the truth is the denial and rejection of religion. How many have I seen who err from the truth because of this high opinion of the philosophers and without any other basis!44

It’s a remarkable record of doubt. “Few are those,” he concludes, “who devote themselves to this study without being stripped of religion and having the bridle of godly fear removed from their heads.” His advice was that only the most wise should read this material, “Indeed, just as the snake-charmer must refrain from touching the snake in front of his little boy,” the wise should not even talk about philosophy among the people.45

Yet, with all his ability to reject philosophy, al-Ghazzali took a long time to convince himself to leave his teaching position to search for truth with the Sufis. The memoir reads a lot like Augustine’s, without the battle with sexual desire. Al-Ghazzali just wanted to stay in the world, in his prestigious position. That’s when “God caused my tongue to dry up so that I was prevented from lecturing.” Worldly desires tugged at him, and he worried that as soon as he gave up his possessions and positions he would wish he had them back. When he finally joined the mystics, he explained that the difference between reading about God and having an ecstatic experience of him is exactly like the difference between reading about alcohol and being drunk. He did this for two years, but because he worried about his family and other responsibilities, he came back into the world and worked in it for another ten years in an “impaired” solitude. Admitting that he had “experienced pure ecstasy only occasionally,” he also said that “innumerable and unfathomable” things had been revealed to him in his periods of solitude. He indicated that there were precise stages of visions and revelations, that those stages could only be experienced; it was impossible to explain in words. Do not try to prove your worldview to anyone through miracles or reason, was the message, for “then your faith is destroyed by an ordered argument showing the difficulty and ambiguity of the miracle.” Go be a mystic and prove the truth to yourself.

In The Incoherence of the Philosophers, al-Ghazzali also argues against the reality of cause and effect, pointing out that nothing about the fact that certain things seem to precede other things is sufficient to prove that the one causes the other—not even “quenching thirst and drinking… burning and contact with fire, light and sunrise, death and decapitation,… relaxing the bowels and taking a purgative, and so forth.” He says his skeptic approach to cause and effect is meant to make room for God, who he insists is the real cause of these effects and who could easily make a decapitated person live, or not allow drinking to slake thirst. But he managed to demonstrate how all rational belief may be reduced to confusion. Al-Ghazzali was a tremendous force in medieval Islam. His biographers attribute hundreds of works to him, and his books were very popular. He had made a cogent claim for the weakness of seeking truth through philosophy, and many followed his lead. Henceforth, until modernity, Muslim theology would be based in authoritative texts and in mysticism, except for one last breath of Aristotelianism. It came so late, in this context, that it did not have much effect among Muslims—but translated into Hebrew and Latin, it was to have quite an influence on humanity over the course of many centuries.

Abu Walid ibn Ahmad ibn Rushd, known to the West as Averroës, lived from 1126 to 1198 and was to formulate a spiritualist rationalism that transformed Western theology and philosophy. Living and working in Morocco and Spain, he did much to bring philosophy back to the West. His commentary on Aristotle was so significant that when Aristotle was translated into Latin from the Arabic in which it had long existed, Averroës’ response to each idea was recopied along with it. Throughout the Middle Ages in the West, for hundreds of years, “The Philosopher” and “The Commentator” meant Aristotle and Averroës. The bulk of Averroës’ work was this commentary, and in physics or metaphysics Averroës differed from Aristotle freely, offering his own interpretations. But first he wanted to be sure he was starting with the real Aristotle. Averroës saw that Avicenna’s Aristotle and Neoplatonism could be separated, and his commentaries on Aristotle consistently show the reader how to disentangle the real Aristotle from what was by then the culture’s common understanding of him. The God that Averroës spoke of, then, was not the Neoplatonic great unity of the universe, which at least sort of jibed with Islam, but rather the Aristotelian prime mover, which did not know the world or its individuals. This last he softened a bit by suggesting that since we do not know anything about God’s kind of knowledge, he may know us in some sense. There was no individual immortality. Averroës teased Avicenna for having conceded too much to Islam.

Along with his commentaries Averroës wrote a number of treatises on philosophical matters, one of which was an answer to al-Ghazzali’s The Incoherence of the Philosophers, which he titled The Incoherence of the Incoherence. Another was a defense of rationalism, also essentially a counterattack on al-Ghazzali’s call for an end to philosophy. As Averroës saw it, the Koran had commanded “Reflect, you have vision” (Koran LIX, 2).46 Based on this “we are under an obligation to carry on our study of beings by intellectual reasoning. It is further evident that this manner of study, to which the Law summons and urges, is the most perfect kind of study using the most perfect kind of reasoning; and this is the kind called ‘demonstration.’” For Averroës, any Muslim who could grasp philosophy must study it diligently. “It is preferable,” wrote Averroës, “for anyone who wants to understand God … to have first understood the kinds of demonstration” and their varying conditions of validity, along with the errors of fallacious reasoning. If someone ended up in a muddle having studied the philosophers, perhaps “owing to a deficiency in his natural capacity,” it was a pity, but it “does not follow that one should forbid them to anyone who is qualified to study them.” Al-Ghazzali’s call to outlaw philosophy “is like a man who prevents a thirsty person from drinking cool, fresh water until he dies of thirst, because some people have choked to death on it.”47

What if philosophy and the Koran clash? Averroës says we have to see that they do not. For instance, Aristotle said the world was eternal and the Koran said God created it—but the Koran did not say how God created it and he may have done so in a way that did not begin at any specific moment. This insistence that demonstrative truth must mesh with the Koran definitely favored demonstrative rationalism. “This being so, whenever demonstrative study leads to any manner of knowledge” the subject is “either mentioned in Scripture or not. If it is unmentioned there is no contradiction.” If scripture does speak of it, “the apparent meaning of the words inevitably either accords or conflicts with the conclusions of demonstration about it.… If it conflicts there is a call for allegorical interpretation of it.”48

When he goes on to explain that allegory is an expanded metaphorical interpretation of something, he asserts that the Arabic language does this of necessity, calling things and acts by things and acts that they resemble. Allegory is everywhere in thought and belief; we just have to figure out where it belongs and to what degree. After all, he says, law is derived from scripture, but everyone knows it has to be interpreted for any given case, and everyone knows it is modified to fit the times. “Now if the lawyer does this in many decisions of religious law, with how much more right is it done by the possessor of demonstrative knowledge!”49 There could hardly be a more important observation in the history of doubt.

Averroës wrote that he was annoyed that al-Ghazzali had spoken and written about such things publicly, and said he was sorry that he had to follow suit in order to refute al-Ghazzali. Averroës thought it best if those of middling intelligence did not know anything about philosophy. But since al-Ghazzali had told the religious that philosophy was a dangerous trap, they hated it, and as a result, philosophers scorned religion in return. Al-Ghazzali had given allegorical readings to the masses, so that they could see that scripture was true in these terms. Averroës said the masses did not need to know about allegory—the masses should simply believe the literal text. Allegories should be discussed only in “demonstrative books” so that they are “encountered by no one but men of the demonstrative class.” Al-Ghazzali, he said, had shown them to everyone because “he wanted to increase the number of learned men, but in fact he increased the number of the corrupted not of the learned! As a result, one group came to slander philosophy, another to slander religion.”50 Averroës was a major early voice in the debate over philosophers’ sharing their doubt with the rest of humanity.

The period of leaning on Aristotle for Muslim theology had passed, but Averroës would have considerable influence on Jews and Christians. Falsafah texts were read throughout the Muslim empire, which included a great many Jews and Christians. It was the Jews who first took inspiration from the Muslims and began a rationalist, philosophical interpretation of Judaism—in Arabic.


Judaism in the medieval period allowed so little doubt that the rabbis told their own Job story, leaving out the whole rebellion. The first speculative philosopher of Judaism was Saadia ben Joseph (or ibn Joseph), who lived from 882 to 942 and counted himself a Mutazili as well as a Talmudist. As a Jew born in Egypt—we are at about five o’clock on the Mediterranean Sea—ben Joseph lived among a great variety of Neoplatonists, Aristotelians, Jews, Zoroastrians, Christians, and Muslims who freely taught their beliefs, argued, and announced final refutations. Ben Joseph suggests that there was a good deal of winking going on already by his time, as people began to doubt that anyone had it right. Charmingly, he cited his own tradition’s ancient doubt in the first paragraph of his Book of Doctrines and Beliefs: “We all seek to probe this distant and profound matter which is beyond the grasp of our senses, and regarding which it has been said by the wise king, ‘That which was is far off, and exceedingly deep; who can find it out?’ (Eccl.7.24).”51 (It was still thought that King Solomon had written Ecclesiastes—which is why ben Joseph calls him “the wise king.”) Before he got going with his philosophy, ben Joseph said that no one, neither the philosophers nor the champions of revealed religion, had based their system on certain knowledge. Everyone was fudging at the edges: people who argue for an infinite universe have never seen anything infinite; people who argue for atoms—for a thing that does not itself have “hot or cold, moist or dry… but which becomes transformed by a certain force and thus produces those qualities”—never saw anything like that. He offers his philosophy as best because, he says, (1) his arguments “are stronger than theirs,” (2) he can disprove his opponents, and (3) he has the testimony of the scriptures on his side.

Although mixed with a great scattering of snippets from the Hebrew Bible, his philosophy has the feel of an Aristotelian argument, but he uses the style to support Jewish doctrine (like creation) over Aristotle. He quotes Job saying things such as “I will fetch my knowledge from afar.” The mythological biblical stories have nothing to do with it, nor the biblical descriptions of God; the only true thing we can say about God is that he exists.52

We do not know whether ben Joseph was the first Jew to write like this, but he was the first we can read. There is evidence that ancient Jews were attracted to all kinds of Greek philosophies, from the Platonic and Aristotelian to the Epicurean, Skeptic, and Stoic, but this evidence is usually in the form of an absent enemy: traditional Jews tell us of their struggle with these people. The closest thing to secular philosophy the Jews had produced was Ecclesiastes, and that sounded more like Epicurus than Aristotle—it advised on our situation; it did not painstakingly work out proofs. Ben Joseph inaugurated the new era in which the way of the Greeks was finally allowed to occupy part of mainstream Jewish thought (this after the heirs of the Greeks had been speaking of the Jewish God for more than a thousand years). Ben Joseph saw the search for philosophical truth as a mitzvah, a religious obligation, and this idea would remain a part of Judaism—and doubt.

Along with the Aristotelians, there were Jewish Neoplatonists in the Middle Ages, too. Solomon ibn Gabriol (ca. 1022–ca. 1051) was outstanding among them. His Fountain of Life was pure philosophical speculation, unconcerned with theology. An odd thing about this book, which was written in Arabic, is that it was preserved only in a Latin translation made in the middle of the twelfth century. Because of the complete absence of biblical or rabbinic citations in it, medieval Christians thought the book was written by a Muslim or a Christian Arab. That this could occur is a bold indication that philosophy had a life of its own in this period. Ibn Gabriol was borrowed from and quoted approvingly by such luminaries as Albert the Great, Thomas Aquinas, and Duns Scotus. Jews, meanwhile, knew him almost only by his poetry.

The most important figure of the Jewish response to Falsafah was Rabbi Moses ibn Maimon—known as Maimonides (1135–1205). Maimonides was a talmudic scholar and a philosopher, as well as a medical doctor of great renown, who lived at the same time as Averroës, both in Cordova, the capital of Muslim Spain—about eight o’clock on the map of the Mediterranean. Like Averroës, Maimonides was thrilled by the ideas of Falsafah and wanted to study deeply to find meaning. Maimonides, however, was run out of Spain by a Muslim sect for being Jewish. The era of Muslims, Jews, and Christians living peaceably together in Spain was going to last awhile, but it was often interrupted. Maimonides’ first books were about Jewish law; his Mishneh Torah was a code of Jewish law intended to guide Jews on how to behave in all situations just by reading the Torah and this code, without having to hunt through the Talmud for specific examples. It became a standard guide to Jewish practice and is still the basis of orthodoxy. In the Middle Ages it was said of him that “From Moses to Moses there was no one like Moses”—he was a religious man and one of the greatest Jewish legal scholars of all time, but he also offered brilliant beginnings to the philosophy of secular Judaism.

His third great work, the famous Guide for the Perplexed, is a key work in the history of doubt. He wrote this book specifically for people who had studied Jewish law and then studied ancient philosophy and who were upset by what philosophy suggested about the anthropomorphic God described in the Hebrew Bible. It is a notoriously peculiar book because Maimonides was living in a world in which secret knowledge was supposed to be kept secret. Thus he explains at the beginning that the book is deep and tricky, not what it seems. Only the deepest and trickiest minds would know what was being said. Not surprisingly, people have been arguing over what the Guide means ever since he wrote it. What Maimonides expressed was essentially a midway position between belief in prophecy and belief in rationalism. As he told it, before he came along the great sages explained our laws and beliefs as such: some have good reasons that we can see, and some have good reasons that are over our heads. Maimonides disagreed. Some of it was for health; some was for politics (such as keeping people scared of divine retribution); and some was for peace of mind, to help you cultivate your higher qualities. As for what God wants, we could not begin to wonder what God wants. Keeping the laws is a simple human thing, and there is no reason to think God cares about it. Maimonides is the first Jew we have on record as giving this kind of secular, political, and psychological explanation for the Jewish way of being. Note also that he echoed the Greek idea of the myths of religion as social control.

Scripture further demands belief in certain truths, the belief in which is indispensable in regulating our social relations; such is the belief that God is angry with those who disobey him.…

In some cases the law contains a truth which is itself the only object of that law.… In other cases, that truth is only the means of securing the removal of injustice, or the acquisition of good morals; such is the belief that God is angry with those who oppress their fellow-men … or the belief that God hears the crying of the oppressed…53

Maimonides was a beloved physician. He regularly worked twelve-hour days tending the crowds of patients who gathered in his courtyard, giving his last prescriptions from a daybed, too tired to stand.

What did Maimonides think about God? Well, he knew that there were “those who do not recognize the existence of God” and instead “believe that the existing state of things is the result of accidental combination and separation of the elements, and that the Universe has no Ruler or Governor.”54 These people, he says, are “Epicurus and his school, and similar philosophers.” But he dismisses them with a wave, “It would be superfluous to repeat their views, since the existence of God has been demonstrated.” Aristotle had this right, and there was no need to worry over it: something “thought” this world into being and put it into motion. For the history of doubt, the key point here is that Maimonides was well aware of Epicurus, of atheism, of other doubters, and of the idea of a world run entirely by chance.

Maimonides was terrific at bearing uncertainties. He was in favor of the Aristotelian idea of the eternity of the universe and also in favor of the biblical creation ex nihilo, and in the end opted for a respectful shrug on the issue. How did he find a space for biblical creation? Aristotle, he explained, had based his conclusion on an analogy between the world we know and the vast universe that is hidden from us by time, space, and our conceptual limitations. There is no reason to hope these are similar enough to bear analogy to one another. He said that Aristotle had only been offering a good guess, a fact most people missed. It is unusual for things to pop into being, yes. But maybe that is how it happened. As for creation, of course it might just be a myth, but all Maimonides held himself to accomplish was to show that Aristotle could, conceivably, be wrong on the subject. By arguing that Aristotle had made a false analogy, from the knowable world to the unknowable universe, Maimonides had accomplished this to his satisfaction. He handled Cicero’s and Augustine’s problem about what God did while waiting around to create the world with Augustine’s answer that time came into being only with the world, as an accidental consequence of motion.

So creation was possible, yet the only good argument for it was that “prophecy” supported it. Maimonides, well informed of the Muslim doctrines reconciling Aristotle with the Koran and prophecy, believed that prophetic knowledge was real knowledge, coming from the imaginative faculty of the mind. His is an awfully human-based, philosophical prophecy, though. Speaking of the idea of God as a creator, Maimonides said, “Abraham our Father was the first that taught it, after he had established it by philosophical research.”55 Abraham the philosopher! Rationalist Jews were now not wrong to believe in creation, and these words were championed by Jews and Christians for centuries. The great love people had for the Guide, generation after generation, suggests that there were a lot of people who would have described themselves as “perplexed.”

Maimonides developed a strange new method for speaking about God. According to good philosophy, we cannot know anything about God other than that he exists, so really, nothing can be said. Maimonides’ idea was to phrase everything one says about him in the negative. “The Torah,” he quotes, “speaks in the language of the son of man,” and it does so to be easily understood. Actually, he explains, we know God has no corporeal body, is not involved with us, and could not be understood in terms of human traits. Of him we may only say: God is not weak, God is not strong, God is not wise, God is not great. To say that he was wise, after all, would be like meeting a king famed for his stockpiles of gold and complimenting him on having some silver. “Is this not an offense to Him?”56

The more thoroughly you negate attributes of God, promises Maimonides, the more you will come close to him, for you will be meditating on his unknowability. Maimonides had a lot of fun showing how one could come to know objects or phenomena, such as a ship or fire, by negativedescription, but here he whittled away at attributes until you knew, for instance, that you had a large, hollow, wooden thing that floats. His point about God, however, was not a clever way to figure out positive attributes. It was a purposeful communing with their absence. The ancient Temple of Jerusalem had had an empty chamber as its holiest shrine. Now the unimaginable became unimaginable in a whole new way. Maimonides said, “Do not desire to negate merely in words.” You have to really mean it. For example: “It follows necessarily that He exists, but not according to the notion of the existence which is in us.” As far as what we mean by existing, God doesn’t.

“He who affirms that God… has positive attributes… has abolished his belief in the existence of the deity without being aware of it.” If someone said that the taste of chocolate is, say, blue, you would not argue about the color, you would explain that taste is not visual. The idea of a God who could be described is completely wrong. In a great device, Maimonides asks us to imagine a man who knows that the word elephant signifies an animal, but nothing more. Now imagine that someone misleads him, saying that an elephant

is an animal with one leg, three wings, lives in the depths of the sea, has a transparent body; its face is wide like that of a man, has the same form and shape, speaks like a man, flies sometimes in the air, and sometimes swims like a fish. I should not say, that he described the elephant incorrectly, or that he has an insufficient knowledge of the elephant, but I would say that the thing thus described is an invention and fiction, and that in reality there exists nothing like it; it is a non-existing being, called by the name of a really existing being, and like … a centaur, and similar imaginary combinations for which simple and compound names have been borrowed from real things.57

God is perfect simplicity. When we apply the name God to something with attributes, “we apply that name to an object which does not at all exist.” That elephant that you’ve got there, it does not exist. Notice that, after the first wacky thing about one leg and three wings, Maimonides just references wacky things that are said about God. Recognize that nonexistent elephant now? For him the world must be the result of some singular essence with the potential for creating patterns, but that’s a far cry from the anthropomorphism of the Bible. It is a pinnacle of Jewish doubt. Maimonides, by the way, quotes Ecclesiastes a lot: “For God is in heaven and thou upon the earth; therefore let thy words be few. (Eccles. 5:1).”58 He finds other encouragement not to give one’s time to prayer, such as Psalm 65:5, “Silence is Praise to thee,” and Psalm 4:4, “Commune with your own heart upon your bed, and be still.”59 Rather than praising God, he advises, “it is… more becoming to be silent, and to be content with intellectual reflection, as has been recommended by men of the highest culture.”60

Maimonides was a practicing Jew, but he explained the necessity of the laws, prayers, and rituals as dependent upon humanity’s inability to bear an utterly abstract, lawless worship of God. People need religion for political and emotional reasons; for ideas our best options are reason, meditation, and resignation. Maimonides saw “the mass of religious people” as “the multitude who observe the commandments, but are ignorant.”61 He argues that when ancient information, either that of Aristotle or the Jewish sages, is contradicted by the growth of a scientific discipline, the ancient information must be discarded in favor of truth. When people asked him what to think about astrology, which seemed like superstition but was backed by numerous talmudic sages, he was not ambivalent. The “entire position of those who predict the future from the stars is regarded as false by all masters of science,” and that, he insisted, means that it is false. He writes that if one searches the Talmud and the Midrash, one can find sages who speak of the stars having an effect on people, but, he says: “Do not regard this as a problem. It is not proper to abandon matters of established knowledge that have been verified by proofs… and depend instead on the teachings of individual sages who may have possibly overlooked what was essential to these matters.… A man should never cast reason behind him, for the eyes are set in front, not in back.”62

Finally, note that Maimonides had an interesting take on two great Jewish doubters. Like everyone else, Maimonides scorned Elisha ben Abuyah, Aher, but he ignored the specific things that the Talmud accused Elisha of believing and doing. Instead, Elisha was characterized as one who believed and did all the things typified by heretics of Maimonides’ own day, and of his Arabic world. These included believing in the eternity of the world and disbelieving the prophets. Sarah Stroumsa has made a good argument that Maimonides was referring directly to Ibn al-Rawandi: Maimonides mentions almost nothing of what the Talmud says of Elisha and instead gives a description that perfectly fits Ibn al-Rawandi.63 It is also possible that Maimonides knew of Jews who themselves enacted these heresies. In any case, he made it clear that he knew of many Jewish unbelievers, speaking of those who “claim to be more intelligent and brighter than the Sages,” and those who “repeatedly mock the sayings of the Sages.” The other curious reading Maimonides offered was on Job. He devotes two chapters in his Guide for the Perplexed to analyzing Job, and repudiates the long-standing rabbinical habit of ignoring Job’s revolt. Instead, the story was said to showcase the maturity Job gained through experience. We should feel the roar of grandeur and not worry “whether He knows our affairs or not, whether He provides for us or abandons us.” Maimonides did not believe in providence or even a God who could speak and act, so he turned the Job story into an allegory for self-control and wonder.

Maimonides had tremendous stature in the late Middle Ages. As his works spread widely through Spain and southern France, they caused a burst of Jewish philosophy that lasted several centuries. The great Jewish mystical movement of Cabala took off in response to Maimonides and other Jewish rationalist philosophers. But there were forms of Jewish mysticism before Maimonides. These had a lot to do with psychosomatic practices such as fasting a specific number of days, getting into odd postures, and whispering or humming precise words and phrases. As the great scholar of Jewish mysticism Gershom G. Scholem has pointed out, mysticism depends on people feeling very separated from God: if there is naïve belief that sees God in nature, and then a period of rationalism that sees God outside nature, the period of mysticism follows only then, as an attempt to get back to this distant God.64 We are reminded of al-Ghazzali. Unlike the philosopher, the mystic does not deny revealed knowledge, but he or she is perfectly willing to generate so much new knowledge that the old is swamped. Mysticism of this kind had a good career in Judaism, perhaps because the orthodoxy never had enough command of worldly state power to stamp it out. Cabala, the great Jewish mysticism, was a mixture of Maimonides’ notion of the total unknowability of God with some ancient Gnosticism, Neoplatonism, ancient mythology from the East, and an earlier, German-Jewish mysticism called Hasidism (it’s been the name of many movements because it means “the devout”). This Hasidism was a system of psychosomatic practices developed to reach states of ecstasy and get a glimpse of God, intended for a select group of seekers.

Cabala had two founders who, although very different, both came to mysticism through Maimonides and who lauded his work even after their own conversions. One was Abraham Abulafia (1240–ca. 1291). He conceived of his mysticism as adding the final step in the Guide for thePerplexed, which he admired deeply. This may have been so, but it was a giant step. What he prescribed was most like Eastern religions of enlightenment. One meditated on the letters of the Hebrew alphabet using methods that were very much like music in their patterns. To cite Scholem again, “his teachings represent but a Judaized version of that ancient spiritual technique which has found its classical expression in the practices of the Indian mystics who follow the system known as Yoga.”65

Moses de Leon, another Spaniard from the same period, transformed Cabala into the tremendous movement it became. His great book, the Zohar, became the central text of Cabalism and, in fact, became a canonical Jewish text. For several centuries it was ranked with the Bible and the Talmud. Here is what we know of the book’s author: In 1264, when Moses de Leon was about twenty-four years old, we have a record of his going to considerable effort and expense to have a Hebrew translation of the Guide for the Perplexed made up especially for him. In the 1270s he became friends with a follower of Abulafia’s Cabalism. We also know he read the pieces of Plotinus’s Enneads known then as The Theology of Aristotle. There de Leon read of the philosopher’s ecstatic rise into the world of truth.

The Zohar was written about 1280, at a time when the Crusades had been ripping through Europe, sometimes decimating Jewish communities along the way. Philosophy had offered a rational interpretation of Judaism, but in difficult times people long for the comforts of religion. The Zohar claimed that Jewish law did not need to be defended rationally at all, for all its gestures were part of the secret-knowledge rites that had to be done to fix the broken world. In this, de Leon seems to have been influenced equally by ancient Gnosticism and Neoplatonism, but such a notion never had a better world of symbols and rituals to invest with meaning. In the sixteenth century the Cabala championed by Isaac Luria would parallel this in Luria’s idea of repairing the “broken vessel” of divine light through acts of kindness. Here in the thirteenth century, Cabala made the acts of Judaism come alive as thrillingly meaningful because according to the Zohar each individual, going through his or her lawful obligations, was mystically fixing the world. Whereas Abulafia’s program was a system of ecstasy for the elite, the Zohar’s program was explicitly for the masses, and intended to revive the doctrines of naïve popular belief that were being challenged by the philosophers.

Meanwhile, the Jewish philosophical movement begun by Maimonides also produced Levi ben Gershom (1288–1344), known as Gersonides, of southern France. We are at about nine o’clock on the Mediterranean map. By the thirteenth century the intellectual language of the Jews had switched from Arabic to Hebrew, and a Hebrew translation of Maimonides’ work had profoundly shaped Gersonides’ world. Gersonides himself was a scientist, an astronomer, and a mathematician. He used a camera obscura to watch eclipses and other heavenly phenomena. The image projected in one of these “dark boxes” can be traced for a precise drawing, but since Gersonides used treated paper, which he later “developed,” he can be seen as having taken the first photographs. Gersonides also invented the “Jacob’s staff,” a pole with metal plates used to calculate angular distances with reference to the stars, which made ocean-spanning voyages possible. This combination of doing theory and technology was almost nonexistent in the Middle Ages. More than anyone else of his time, Gersonides emphasized the need for empirical observation as a basis for astronomical research, rather than just theorizing with past observations and conjecture.

He seems to have been the only person to falsify the Ptolemaic, Earth-centered model of the solar system. He may have gotten the idea from reading Maimonides, who had mentioned that there was no way to verify the odd epicycles Ptolemy described. Gersonides used his camera obscura to check if the brightness of Mars varied in ways that supported the idea of the planets moving in epicycles. It didn’t. He tried to come up with an alternative model but couldn’t. Not even Copernicus, Kepler, or Galileo, who would solve and resolve the riddle three centuries later, ever offered a falsification of the old model. This side of the story is almost never told, but we are interested in doubt, not merely new solutions. Gersonides put the matter into question, and knowledge of his work may have helped lead Copernicus in the right direction. In the twentieth century, these contributions were recognized by the naming of a lunar crater after Gersonides, which has earned the fourteenth-century scientist the moniker of “the first rabbi on the moon.”66

Gersonides approached philosophy and religion in a similar way. Along with his science, he was also famous for centuries for his superscript commentaries on Averroës’ commentary on Aristotle. He did not agree with the philosopher on all matters, but he came to agree that God had no knowledge of the goings-on of life. Aristotle had persuaded Maimonides of almost this much: Maimonides had lived as an observant Jew, but philosophically he did not believe that God could be thanked, praised, or petitioned. There was an essence to the universe and perhaps it had some sense of us and some benevolence; for Maimonides, this was the force at the heart of the Jewish religion, even if a lot of mythological ideas had been necessary for ancient people to believe. By contrast, Gersonides’ God could be said to know of us only insofar as his pattern-full essence is what we are. “For God does not acquire His knowledge from them; rather they acquire their existence from His knowledge of them, since their existence is an effect of the intelligible order pertaining to them inherent in the divine intellect.”67 Notice that there is no divine thinking implied here.

His dedication to rationalism was a matter of personal conviction and he could cite authorities for his right to it:

There is nothing in the words of the Prophets that implies anything incompatible with the theory we have developed by means of philosophy. Hence it is incumbent upon us to follow philosophy in this matter. For, when the Torah, interpreted literally, seems to conflict with doctrines that have been proven by reason, it is proper to interpret those passages according to philosophical understanding, so long as none of the fundamental principles of the Torah will be destroyed. Maimonides too follows this practice in many cases, as his famous book the Guide for the Perplexed shows.68

With God so distant, unknowable, and unknowing, and the Torah disprovable just up to the point that it not be destroyed, we have come rather far into Jewish doubt.

The balance that existed between Jewish mystics and Jewish rationalists was about to change. There was fatal pressure on Spanish Jews to convert, beginning with massacres in 1391, and eventually there was a population of people who were secretly still Jews, called Marranos. The Spanish Inquisition was all about ferreting out these people. When King Ferdinand and Queen Isabella finally finished kicking the Muslims out of Spain, they turned again to consider the Jews. The Jews had a rich and complex society in Spain, going back hundreds of years; Spain is as much the home of Jewry as the Middle East and Eastern Europe. In 1492 the Jews of Spain were given three months to leave or convert. How could a world leave? The departing Jews lost almost all their property. The king of Portugal offered safe haven at a price and a great many Jews took him up on it. After he got the money, he began selling the Jews into slavery or otherwise dispatching them.

After a long period of almost idyllic coexistence, the Jews of Spain were subjected to sudden and horrific persecution. Many died of starvation on the outskirts of some Christian town, in a foreign land. All lost their world, with its million ancient delights, exquisite mosaic synagogues, songs, recipes, literature, and jokes. Cabala was transformed through this awful rupture, so that it described everything in the Bible and in Jewish life in general as being about exile and return. The Zohar stressed acts of repentance and “savoring” the bitterness of exile. In the Cabalist image of Job in this period the fate of humanity rested on Job’s ability to bear his suffering. For the exiled Jews of Spain, the idea that the pain of one person’s life could have cosmic results, even if one did not believe in providence, was obviously appealing. Eventually, sometimes after generations, many Marranos made their way to better lands—they or their descendants founded the Jewish communities of Amsterdam, New York City, Hamburg, and London—where they returned to a public, common Judaism that was by then fascinatingly foreign to them. Eventually, these communities would be fertile fields for doubt. After the disaster of 1492, though, Judaism grew increasingly mystical. Doubt closed down in Jewry as it had closed down among the Muslims. But not before tipping the flame toward one more culture—the Christians.


When we left Christian Europe at the end of the ninth century, Charlemagne’s cathedral schools were poring over Boethius’s logic. Those educated at the schools learned how the world worked through treatises on Plato, Aristotle, Cicero, and the Stoics that had been written by early medieval thinkers such as Isidore of Seville and the Venerable Bede. Finally, the cathedral schools’ natural philosophy was based almost entirely on the Timaeus of Plato, which, as we have noted, was embedded in a commentary by Chalcidius and, moreover, was only partially translated. That is all they had; the East had the good libraries and the Arabs had the East.

Nevertheless, this world was developing its own pitched battle between rationalists and mystics, and they were somewhat influenced by the outside world. Here the rationalists were Anselm of Canterbury (1033–1109), the one with the famous proof, and Peter Abelard (1079–1142), the one with the biography that makes everyone wince. Against them was the amazing mystic and musical composer Hildegard of Bingen (1098–1179). It was an even fight. Anselm’s proof of God was that we have an idea of a perfect God, but reality is always better than something that is not real, so God, being perfect, must be real. It did not take long for people to point out that, actually, we cannot make a three-course meal appear by imagining a perfect one. Still, much Christian faith was tending toward rationalism, proofs, and demonstrations. The same is true for Abelard—he was not a doubter but is of passing interest to our story as a rationalist in the service of faith. He also came to a keen understanding of Aristotle, more than had been understood in his world in centuries. Here’s the wince: He is best remembered for seducing and then secretly marrying Heloise, one of his students and the daughter of an important Paris churchman. When he would not live openly with his wife, her relatives castrated him. He then went off to a monastic community and she to a convent, from which they exchanged many letters and further developed their reasoned faith.

I said above that the battle between philosophy and mysticism was a fair fight. The mystical side was well covered by Hildegard, whose career provides a demonstration of what doubt was up against. Born to a noble family in Germany in 1098, Hildegard was only eight when she was sent to a wealthy Benedictine convent. The place was run by a famed mystic abbess called Jutta, and this woman raised Hildegard herself. The girl eventually succeeded Jutta as prioress, leaving after a while to start a convent closer to the ideal of poverty, near Bingen. Hildegard’s noble pedigree and her famous mentor gave her status, and she was an incredible talent. She said she had had visions from a young age, and she wrote tomes full of vibrant allegorical visions and charges of impiety.

Saint Bernard of Clairvaux, the twelfth-century monastic reformer, read her work and the two became fervent correspondents. Bernard secured the pope’s approval of Hildegard’s theology. He also got the pope to condemn some of Abelard’s rationalist propositions. Hildegard was soon traveling all over Germany lecturing monks, clergy, and secular officials, recounting her visions and scolding them for their carnal transgressions. She also wrote well-respected medical treatises. In person, too, she had a great following, who came to her for counsel. She is often described as the most profound psychological thinker of her day. Marvelously, that’s not the half of it, for she is the first composer in the West whose biography is known to us, and her music, which took the form of ethereal angelic chants, is still played today. She also invented the morality play.

So there were attractions to philosophy and there were attractions to mysticism. This balance was about to change. About the year 1000, weakness in the caliphate of Cordoba encouraged the Reconquista, the “taking back” of Spain for the Christians (the Visigoths had been there before the Muslims; they were a heretical, Christian, Germanic tribe). Over the next centuries the Reconquista brought the new ideas in Muslim and Jewish Spain to European Christians. There were major centers of learning in Toledo and Sicily, and for most of the eleventh century these were still out of reach of the Christian world, which knew the Muslims had vast knowledge far beyond its own. King Alfonso of Spain, aided by the dashing mercenary warrior El Cid, managed to take Toledo in 1085. In 1091, the Normans took Sicily. Throughout the twelfth century, scholars ran to these two destinations to find works in Arabic, and to several destinations in Italy for works in Arabic and Greek. Many of the works they got their hands on already had hairy translation histories.

It was mostly science that made the loop-the-loop around the Mediterranean, not literature. In this wave, once again, a handful of translators changed the world. Gerard of Cremona (died 1187) translated from Arabic to Latin: Aristotle, Ptolemy, Euclid, Galen, al-Razi, and Avicenna. In all he translated about seventy books. A little later, William of Moerbeke (ca. 1220–1286) translated from Greek to Latin almost all of Aristotle and Archimedes, and a great variety of commentators. He translated about fifty works. Western Europe had never been thrown that much new stuff. Historian Edward Grant says, “The impact of Euclid’s Elements and Ptolemy’s Almagest alone were capable of transforming the basis of science. It was as if the West had left a barren desert and moved to a richly watered oasis.”69 Grant is one of our best authorities on the Middle Ages, and his book God and Reason in the Middle Ages offers wonderful evidence about the prominent role of reason in these misunderstood centuries.

As Grant explains, it was the new texts of Aristotle and Aristotelianism that really changed everything. The great philosopher had written out rules and a method for all sorts of disciplines. In the culture of the Europeans of that time, these realms of thought were just a mishmash of vague and contradictory notions. Aristotle told how the Greeks had climbed out of impressionistic and mixed-up thinking and laid out the foundations for clear thinking: logic and observation. His sheer range and output were staggering, and by now there were numerous Greek, Latin, and Arab commentaries that treated him as the great authority. Europe was transfixed by this work. It was the eleventh hour on the Mediterranean doubt clock. The rivalry with the mystics ended in a flash because the new, almost magically sophisticated math, medicine, and science simply blew it out of the water.

By this time, cathedral schools had been thriving in various urban centers, such as they were, for a few centuries. For their own protection and to create a more coherent community, they began to get themselves incorporated, as did almost every other distinct group in the Middle Ages. Being incorporated meant that the group had certain rights and privileges and had to abide by laws. The Latin word most commonly used for these incorporations was university—the reason the word means “school” now is because the school-type university is the only one that made a successful transition from that time to our own. The incorporations set up the universities to do a certain amount of teaching in a certain way. So after they were incorporated, they needed a lot of curriculum material, immediately. As it happened, the ancient texts that were rediscovered at this time were almost all about logic, science, and math. Thus the universities, which had different specialties—law here, medicine there—all had a huge preliminary curriculum, which included four to six years of logic. The absence of ancient texts on theater, poetry, history, and other branches of the humanities made this a very rationalist course of study. The curriculum of the arts degree was Aristotle’s natural philosophy and it remained so across half a millennium. Theology, medicine, and law were above the arts degree, being more important and later in one’s education, but that meant that everyone had to first earn the arts degree.70 Thus, logic (four to six years of it!) provided the one common ground of all these scholars, theologians, and practitioners, and for all of them it provided the foundation of their worldview.

They did just what you would think a somewhat-literate tribal world would do, if, as it was naturally developing some rational rules for knowledge, it suddenly found a cache of the finest thinking of an ancient world that had dedicated itself to rational wisdom. They fetishized it. They did not use it to look for new knowledge or for ways to make things, move things, or take things apart. They merely tried to make sense of the material they had found. Consider this: they never thought to understand Aristotle’s works as the changing thoughts of a man across his lifetime—they simply followed the Muslims’ lead and worked to posit an explanation for the “discrepancies.” Since the cache of ancient wisdom they found was a very particular corner of all ancient thought, they made a world of a molehill.

The medieval scholars faced the varied genius of the new Aristotle, Euclid, Ptolemy, Hippocrates, Galen, Avicenna, Averroës, and al-Razi and blinked at the variety of claims. They met the challenge of this avalanche of opinion by writing out yes or no questions and then arranging the opinions of the great thinkers for and against. This was the gist of the Scholastic method, and those who did it were called Schoolmen; they were the Church’s philosophers, the rationalist theologians. A question might be “whether there could be an infinite dimension” and then a “principal argument,” which stood as a bit of a straw man, and then “Aristotle determines the opposite” or “The Commentator affirms the opposite” (Averroës, of course, being “The Commentator”), and then the author’s opinion and reconciliation of any remaining problems.

I have said that the new Aristotle that came in, mostly in Arabic, was like a typhoon, overtaking mysticism. It also knocked out Boethius in one swipe. He’d had an incredible run. Boethius’s labors maintained the discipline of logic for half a millennium. The reason people knew what it meant to find a whole cache of Aristotle, the reason that name cried out to Europeans when they saw the Arabic letters spelling it out, was because of Boethius.

The most important of all the new texts was Aristotle’s Sophistic Refutations. It was a study of fallacy: how words work and what to call the ways in which they can be deceiving. It appeared in Latin about 1120 and just plain took over. For one thing, it was easier to understand than others, and for another, it offered instruction about work that was yet to be done and how to do it. The Schoolmen picked it up with glee. They started to take apart language to see how it worked so they could be sure of speaking the truth—there were treatises, for instance, on syncategoremata, words that cannot be subjects (such as: every, because, and, or, if), which made logicians suspicious of sentences with such words in them. In fact, the way that Latin words worked soon became more important than their content. What is more, although word order is unimportant in Latin, the Schoolmen assigned meanings to Latin word order and thus expanded their project. That is, the Schoolmen learned from Aristotle that this conceptual game of logic could be used to negotiate fallacies and they turned Latin into a symbolic logic system, rather than a system of communication. The Schoolmen thus used purposefully silly content, so that content would not distract them. That is why it has seemed like such hocus-pocus to the later Europeans.

Apparently a sentence was constructed so that one could argue that it was true and then argue that it was false, and the idea was that one would learn something, or hone one’s truth-finding skills, by analyzing these claims.71 Scholastic authors liked citing famous ancients in their content-nonsense texts. Consider some of their sentences:

Varro, though he is not a man, is not a man, because Cicero is not Varro. A head no man has, but no man lacks a head. Socrates is whiter than Plato begins to be white. Socrates will as quickly have been destroyed as he will have been generated. A horse is an ass. God is not. No man lies. Some horse does not exist. What Plato is saying is false. Socrates wants to eat.72

A variety of exercises and games were being worked on here. Sophisms were one major project of these weird statements. Sophisms were arranged in themes. That is, they were understood to exemplify, for example, themes of signification, supposition, connotation, and insolubles. The sophism “This dog is your father” is true and intelligible because the dog is yours and the dog is a father; you own this father; this dog is your father. The best here are the insolubles, the most famous of all being: “What I am saying is false.”

Scholasticism, then, was not at all religious in the sense that people think of Scholasticism as being religious. No one argued about how many angels danced on the head of a pin—people made that up later to deride the Schoolmen. True Scholasticism was not experimental, nor did it seem to be about finding any new knowledge, yet it is not right to see it as a religious game of faith-blinded theologians. These were the thinking people of the age, they were very educated, and they did not all simply take Christianity as literally true, on faith, en masse. They knew of other religions and even of a whole non-Christian past. They were curious about things other than those within the prescriptions of their religion, and working on their weird Scholastic sentences led them to some subtle and interesting philosophical questions.

When the Schoolmen’s logical investigations brought them to a wall around which their faith would not allow them to peer, they usually found a way to peer anyway. To get a taste for their rationalism, consider that the Schoolmen had a whole branch of thought dedicated to “the first and last instant.” Aristotle had wondered whether there was a moment in which something can truly be said to become something else, or is the continuum the only reasonable way to think about change? If so, how can we speak of things starting and stopping? The Schoolmen followed him and asked about the outside possibilities of things in the world. They asked themselves questions such as “Should a capacity such as Socrates’ ability to lift things be limited by a maximum weight he can lift or by a minimum weight he cannot lift?”

They did not leap from reading Aristotle’s arguments into making entirely different arguments of their own; they stayed close to his, disagreeing here and there but generally remaining pretty impressed. Indeed, they praised his empiricism without actually doing anything experimental or empirical. Yet, as we have seen, there is a way in which Aristotle was not very experimental either. Compared to Plato, who did not trust the senses and thought the world was to be perceived through ideas, Aristotle had been very empirical, it was true. Observation and experimentation were seen as the route to truth. Yet Aristotle had a definite gut feeling that the world was a noble, coherent whole: in On the Heavens, On the Soul, Physics, On Generation and Corruption, he was dedicated to figuring out the world honestly, but his conviction that it was all going to make beautiful sense made him look for ways for it to fit together conceptually. The Schoolmen mostly did what Aristotle had done, but with almost no actual observation of the world: they occupied themselves with discussing his observations. After all, Avicenna and Averroës and all the others had treated Aristotle (or rather the philosopher they knew as Aristotle) as the ultimate authority. That tradition went back many centuries now.

No one in Christiandom seems to have done any physical experimenting across these long centuries. What they did was to follow Aristotle’s lead with a lot of thought experiments. One of the best known was about a bean. Aristotle had said that if a thing is thrown up and then comes down, there is a moment of rest in between. Here’s the question the Schoolmen got hung up on: Imagine a bean thrown up just when a big stone is thrown down. If at the moment of contact the bean did in fact stop (in order to begin descending), it would have to hold up the stone, which is impossible. By thought experiments such as this, they did actually derive the “mean speed theorem” in their inquiry into the concept of variation. They also came up with impetus theory, the possibility of finite motion in a vacuum, and the idea of void space outside our cosmos. As Grant points out, “We may properly characterize medieval Aristotelianism as empiricism without observation. It was also empiricism without measurement.”73 John Murdoch has called it “natural philosophy without nature.”74 What would you expect from a world suddenly faced with advanced schools of thought from a culture not its own? Had they been recipes from another world, set in conceptual terms far beyond us, they might have been recited as poems for centuries before anyone thought to get out the pots and pans. Scholasticism was not science, but it was more rational than religious.

It was this period that saw the rise of Padua as a center of science and Averroën Aristotelianism. Albertus Magnus, Albert the Great, lived most of the 1200s and was one of the best theologians of the Middle Ages. He was educated at the university of Padua and joined the Dominicans while still a young man. When his Dominican brothers asked him to write a book explaining the “science of nature” to them, they specified that they wanted it so that they could attain at least a competent understanding of Aristotle. As Albertus explained in the introduction, “we take what must be termed ‘physics” more as what accords with the opinion of Peripatetics than as anything we might wish to introduce from our own knowledge.”75 In discussing whether the heavens were made out of nothing or generated from something, Albertus made it clear that in the “principles of nature” things are always generated from other things. Thus, despite its being contrary to his faith, it was only this option that was worth considering in his Physics.

At this same time we find the French theologian Siger de Brabant (died ca. 1284) being called “head of Latin Averroism,” which was based at the universities of Paris and Padua. In Paris, Siger taught that the individual soul had no immortality and that the world was eternal rather than created. When asked if he could still be a Christian with these notions, Siger showed that he believed he was following the Averroist idea that different intellects could handle different versions of the truth. Actually, he had perverted this notion a bit, arguing that there could be “two truths,” that is, that something could be true in rational philosophy but false in religious belief.

Thomas Aquinas came on the scene in a fierce attack on Siger. Indeed, Aquinas’s work was in large part an attempt to defend both Aristotle and Christianity from the stark separation that was being made here between philosophical believers and popular believers. He wrote a number of commentaries on Aristotle—on ethics, physics, politics—and these have long been considered among the finest philosophy. “Rabbi Moses,” as he called Maimonides, was one of his major sources. As for his own opinion of God, Aquinas was a bit of an Aristotelian here, too, but he felt that on this one issue, revelation had made a big difference. Consider the first two questions of his most famous work, the Summa Theologica. Question One asked “whether, besides the philosophical sciences, any further doctrine is required,” and showed how one could argue that nothing further is required. He settled in on yes, we do need revelation. Question Two was on “the existence of God” and asked whether it was self-evident. Aquinas noted that since Psalm 14 says “The fool said in his heart: there is no God,” God’s existence is not self-evident.

The third part of that question asked “whether God exists.” Aquinas included this argument against: “If therefore, God existed there would be no evil discoverable; but there is evil in the world. Therefore God does not exist.” He also included this little beauty: “It seems that everything we see in the world can be accounted for by other principles, supposing God did not exist. For all natural things can be reduced to one principle, which is nature; and all voluntary things can be reduced to one principle, which is human reason, or will. Therefore there is no need to suppose God’s existence.” These are an amazing pair of statements, whether or not they are offered as straw men. Aquinas’s answer to them is to cite revelation—“I am Who am”—and to give philosophical proofs: we need a first cause, we need a prime mover, the world shows gradation in its creatures and things and that suggests a perfected being at the top, and finally, the governance of the natural world. The new Aristotelians had seemed hostile to the Church before Aquinas. He offered the Church an Aristotelianism that, by comparison, supported Church doctrine. It was a deal the Church would heartily defend for centuries, but it did not seem like that at first: Aquinas’s work was also repressed, briefly, in the years just after his death in 1274.

After a few preliminary warnings and condemnations, in 1277 the Church became so uncomfortable with the new thinking across Europe—especially at the university of Paris—that it issued a condemnation of 219 propositions, including, for instance, that “the first cause could not make several worlds.” It’s funny enough to hear the Church quoting Aristotle so fully that it calls God “the first cause,” but the point was that the Church had an all-powerful God and it was not going to accept Aristotle’s “impossibles.” Another condemned teaching was that “God could not move the world with a rectilinear motion; and the reason is that a vacuum would remain.” Aristotle did not believe in vacuums, which meant God could not make one, which meant God could not move the world, because it would leave a vacuum. The Church answered that God can do anything. Aristotle had also made it clear that God could not make an accident exist without a subject—it is a logical contradiction. The Church said God could do it, and we can see why: with the Eucharist they had a substance that was transformed into God, but still seemed to have the accidents of the bread. The Church needed to keep some wiggle room around an adjective and its noun so that the accident of the eucharistic bread could exist even though the bread was gone (replaced by the body of Christ, which has no accidents).

As wild as this is, it went further. In 1277 the Church said it was now forbidden for anyone to say the following:

152. That theological discussions are based on fables.

40. That there is no higher life than philosophical life.

153. That nothing is known better because of knowing theology.

154. That the only wise men of the world are philosophers.

175. That Christian Revelation is an obstacle to learning.

37. That nothing should be believed unless it is self-evident or could be asserted from things that are self-evident.

As eminent historian Etienne Gilson put it in 1938, “The list of those opinions is a sufficient proof of the fact that pure rationalism was steadily gaining ground around the end of the thirteenth century.”76 These Averroists went much further than Averroës. “As a matter of fact,” wrote Gilson, “it was like nothing else in the past, but it anticipated the criticism of the religious dogmas which is a typical feature of the French eighteenth century.” Gilson further remarked, “That the so-called Revelation is mythical in its origin is everywhere suggested in Fontenelle’s History of the Oracles (1687); Fontenelle was a very prudent man; he was merely suggesting what he had in mind; but four centuries before him, some Averroists had clearly said it.” I’ll discuss Fontenelle when we get to him later in the book, but it’s useful to consider Gilson’s conviction here. Historians tend to be very touchy about the possibility of medieval doubt. Grant writes, “It is doubtful that any natural philosophers actually incorporated such explosive and potentially dangerous articles into their written work,” allowing only that “If such assertions were actually made, they were probably communicated orally around the University of Paris.” We cannot know for sure, but let us think of that list again: no higher life than philosophical life; theological discussions are based on fables; Christian Revelation is an obstacle to learning. This was an active polemic, a real fight, between real opponents. There were doubters at the Sorbonne in the thirteenth century.

The same list of condemned teachings also included: “that God could not make anything new,” “that there is more than one prime mover,” “that eternity and time have no existence in reality but only in the mind,” “that nothing can be known about God except that He is,” “that God does not know things other than himself,” “that after death man loses every good,” “that raptures and visions are caused only by nature,” “that happiness is had in this life and not in another,” “that there are fables and falsehoods in the Christian law just as in others,” “that a philosopher must not concede the resurrection to come, because it cannot be investigated by reason,” and my favorite, “that man could be adequately generated from putrefaction.” How did the Schoolmen come to all this?

We know they read Aristotle, Averroës, and Maimonides. Not only were many of the Schoolmen believers in a very philosophical cosmos, but after Aristotle had been used as a textbook for centuries it was just beginning to dawn on Europeans that Aristotle and the other ancient writers were not exactly the early texts of the Schoolmen’s own, European civilization. With astonishment, it was slowly being recognized that Aristotle and Plato and the rest of them belonged to a fully other civilization that had its own answers to the big questions and that explicitly rejected a God like Jesus. Not only that, but all these ancient texts had come in from Muslim and Jewish sources, having been transformed by Muslim and Jewish sages, and the shock of confrontation with cultural diversity came from that direction as well.

The result of the Condemnation of 1277 was in part to spur rationalism in new directions. The Schoolmen’s questions about how God could, in fact, do Aristotle’s impossibles fostered among them an imaginative and bold inquiry into questions that their Christian cosmology would never have imagined alone, and that their Aristotelianism would never have imagined either. Aristotle had said that there could not be any other worlds. The Schoolmen did not believe that God had made any other worlds, but they defended the idea that he could. That made them write about the issue, intensely. After the Condemnation they generated ways that God could make a vacuum, ways that other worlds might exist, ways in which the heavens might have been animated by God at the moment of creation and never since. This last was posited against Aristotle’s certainty that since the movement of the heavens was not slowing down, it must be continuously animated, and therefore the stars had souls. Dutiful Schoolmen argued that a really powerful God could do anything, including setting up a universe that runs on its own. As Grant has said, “The invocation of God’s absolute power made many aware that things might be quite otherwise than were dreamt of in Aristotle’s philosophy.”77 Yet, as Grant shows, few questions even mentioned God in passing, and only a tiny fraction dealt with the idea of God as a central issue.78 Theology was becoming a mix of logic and natural science that left very little room for anything spiritual. The Condemnation of 1277 didn’t do doubt much harm and it did the history of doubt a lot of good: just as with the Carvaka and the Hellenistic Jews who opposed the Maccabees, the best evidence of the existence of medieval doubt is what was preserved in the polemics of its enemies—everything else having been burned or only whispered in the first place.

In the fourteenth century, Christian theologians and scholars grew more rationalist on the one hand, and more skeptical on the other. The arts master John Buridan (ca. 1295–ca. 1360) explained that to think about the world as Aristotle did was to reject recourse to the supernatural and to try to figure things out as they appear. There were ways of imagining God doing all sorts of seemingly impossible things, he explained in one discussion, “But now, with Aristotle, we speak in a natural mode, with miracles excluded.” Around 1370 the great theologian Nicole Oresme wrote:

I propose here, although it goes beyond what was intended, to show the causes of some effects which seem to be marvels and to show that the effects occur naturally, as do the others at which we commonly do not marvel. There is no reason to take recourse to the heavens, the last refuge of the weak, or demons, or to our glorious God as if He would produce these effects directly, more so than those effects whose causes we believe are well known to us.79

The heavens, the last refuge of the weak! The period’s other great Christian thinkers—William of Ockham, Duns Scotus, and Nicholas of Autrecourt—pushed into Skepticism, each questioning the ability of reason to describe reality. Ockham even rejected Aristotle’s proof of God.Ockham’s famous question was, How much can reason know faith? His answer was “not at all.” His even more famous “Ockham’s razor” was part of his contribution to logic, and calls for using the simplest explanation possible in all things. Along different lines, Scotus, too, forwarded the notion that reason could not penetrate beyond the world of sense experience and seemed to question whether clear thinking about metaphysics could be done at all. Nicholas of Autrecourt (born ca. 1300) went as far as the ancient Skeptics, the Carvaka, and the Muslim al-Ghazzali on the question of cause and effect: we can never be certain if two rational notions are causally related, no matter how well they seem to link.

Nicholas was sentenced to burn all his writings, and did so in November 1347. Two letters to a friend survived and an excerpt from one will demonstrate the state of doubt:

Just as you do not know whether the Chancellor or the Pope exists… [s]imilarly, you do not know the things of your body—whether or not you have a head, a beard, hair, and so forth.… I wonder very much how you can say that you are evidently certain of various conclusions which are more obscure—such as concern the existence of the Prime Mover, and the like—when you are not certain about these things which I have mentioned.80

A few sentences down he says, “And it seems to me, the absurdities which follow on the position of the Academics, follow on your position.” Nicholas thus knew of the Academic Skeptics even if he only mentioned them to deny them, saying he himself would stick with the evidence of the senses. Elsewhere, he explains that, despite reasons to doubt one’s perceptions, such as the problem of dreams, some things are more probable than others. He is often called the “medieval skeptic.” We have found two Latin translations of Sextus Empiricus from this period (one late thirteenth century, one late fourteenth).81 With a little help from the ancients, the medieval philosophers had arrived at a similar conclusion about philosophy: with it, we always get to the point where we cannot know anything. Not ourselves, not the world, and not God.

Just around the time Nicholas burned his books, big things were going on in Italy. In 1345 Francesco Petrarch stumbled upon something he had been searching for in monasteries and libraries for years: a volume of lost letters of Cicero. They astonished him. The Cicero he found there was nothing like the Cicero everyone thought they knew—the calm, unflappable philosopher. The letters themselves were a form that had not been seen in centuries; the medieval letter was very formal whereas Cicero’s were personal, friendly, conversational, and meandering. We date the start of the Renaissance from this moment, this sudden and profound recognition that Cicero was not the disembodied voice of one branch of philosophy but a man with a personality, an individuality; that culture made all the difference in understanding a life, and that culture changes. The idea was powerful. The hour hand of medieval doubt, roaming around the Mediterranean, had inched up on twelve since Greek skepticism and rationalist doubt were reintroduced to Florentine culture. When Petrarch found Cicero, it was noon in Florence, and the town began to bloom. In the next chapter we will see the old Scholastic Aristotle cursed in favor of Cicero, whose casual tone and nonreligious concerns about human happiness inspired a whole new manner of thinking: Humanism. It was no attack on God, but as is clear from its name, it had a different central concern.

Doubting Muslims, Jews, and Christians had been having a very civilized conversation with each other—and with the ancient Greek and Roman philosophers—for centuries. The conversation was informed by rationalist convictions of human unity, and by the insistent relativism of a cosmopolitan experience, so it was relatively open. There were a lot of doctors, scientists, and community leaders involved.

What we learn in the rationalist loop-the-loop around the Mediterranean is that there was doubt somewhere around the Mediterranean throughout the Middle Ages. In late antiquity it passed from the crumbling world of the now Christian Romans, east to the Nestorian Christians, south to the Muslims and west across their North African world, then north to the Jews of Spain, and back to the Christians of Europe. In the next chapter, after a look at the Far East, we will see Petrarch and others damn the Schoolmen and their beloved Aristotle for being cold, arcane, and no longer relevant. That attack described Scholasticism as an intellectual game of interest only to its players. As time went on people assumed that the arcane Church philosophy was about Christian dogma. In general, the Middle Ages would increasingly be described as hopelessly entrenched in the fables of faith. We have seen that this was not the case. There were doubters, there were rationalists, and there were skeptics.

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