IV. IS MAN A MACHINE?

Yes, said Julien Offroy de La Mettrie. Born in St.-Malo (1709) to a prosperous merchant, he received abundant education, and decided to be a poet. His father recommended the ecclesiastical profession as less perilous; he sent Julien to a college at Plessis, where the boy became an ardent Jansenist. But a doctor friend of the father thought (as Frederick the Great put it) that “a mediocre physician would be better paid for his remedies than a good priest for his absolutions.”44 So Julien turned his zeal to anatomy and medicine, received the doctor’s degree at Reims, studied under Boerhaave at Leiden, wrote several medical treatises, served as surgeon in the French army, and saw “one per cent glory and ninety-nine per cent diarrhea”45 on the fields of Dettingen and Fontenoy. Himself bedded with violent fever, he claimed, on recovery, that the clearness of his thinking had varied with the height of his fever; from this he concluded that thought is a function of the brain. He published these and allied ideas in 1745 in Histoire naturelle de l’âme.

We cannot know what the soul is (ran the argument), and we do not know what matter is; we do know, however, that we never find a soul without a body. To study the soul we must study the body, and to study the body we must investigate the laws of matter. Matter is not mere extension, it is also a capacity for motion; it contains an active principle, which takes more and more complex forms in different bodies. We do not know that matter has of itself the power to feel, but we see evidences of that power in even the lowest animals. It is more logical to believe that this sensitivity is a development from some kindred potentiality in matter than to ascribe it to some mysterious soul infused into bodies by a supernatural agency. So the “active principle” in matter evolves through plants and animals until in man it enables the heart to beat, the stomach to digest, and the brain to think. This is the natural history of the soul.

The chaplain in La Mettrie’s regiment trembled at this conclusion. He sounded an alarm, and the medicophilosopher was dismissed from his post as surgeon. His fellow physicians might have come to his aid, but he had written about the same time a little book,The Politics of Physicians, satirizing their intrigues in competition for lucrative posts. They joined in denouncing him; he found both his practice and his reputation ruined. He fled to Leiden, wrote another attack upon the medical profession, and turned to philosophy.

So at Leiden in 1748 he issued L’Homme machine. By the term machine La Mettrie means a body whose actions are due entirely to physical or chemical causes and processes. That the animal body is a machine in this sense is clear to him from a hundred phenomena: the flesh of animals continues to palpitate, and their intestines continue peristalsis, for some time after death; muscles separated from the body contract when stimulated, and so forth. Animals, then, are machines; and if so, why not men, whose bones, muscles, tendons, and nerves are so remarkably similar to those of the higher animals? The mind obviously depends upon the physicochemical operations of the body. Opium, coffee, wine, and diverse drugs do not merely affect the body, they can alter the stream and character of thought, the mood and force of the will. Change a few fibers in Fontenelle’s brain, and you make him an idiot.46 Bodily disease can weaken the mind; “the soul gains vigor with the body, and acquires keenness as the body gains strength.”47 Diet influences character; so “the English, who eat meat red and bloody, and not as well done as ours, seem to share more or less in the savagery due to this kind of food.”48 “Should we, then, be astonished that the philosophers have always had in mind the health of the body in order to preserve the health of the soul?” and “that Pythagoras gave rules for diet as carefully as Plato forbade wine?”49 And La Mettrie concludes:

Since all the faculties of the soul depend to such a degree on the proper organization of the brain and of the whole body, … they are apparently but this organization itself; the soul is clearly an enlightened machine … Soul is therefore but an empty word, of which no one has any idea, and which an enlightened man should use only to signify the part in us that thinks.50

In L’Homme plante (1748) La Mettrie developed the “great chain of being” into a theory of evolution. He lost some of his confidence when he tried to bridge the apparent gap between the inorganic and the organic; suddenly he forgot mechanism, and slipped into vitalism: he supposed certain semences, seeds, which enabled matter to beget life.51 After that he found it easy to follow Lucretius: “The first generations must have been quite imperfect; … perfection could not have been the work of a day in nature, any more than in art.”52 To diminish the gap between animals and men, La Mettrie argues, against Descartes, that some animals reason:

Let us observe the ape, the beaver, the elephant, etc., in their operation. If it is clear that these activities cannot be performed without intelligence, why refuse intelligence to these animals? And if you grant them a soul, you are lost.… Who does not see that the soul of an animal must be either mortal or immortal, whichever ours is?53

There is no great difference between the simplest man and the most intelligent animal. “Imbeciles … are animals with human faces, as the intelligent ape is a little man in another shape.”54 La Mettrie adds, with his peculiar humor, that “the entire realm of man” is “but a composite of different monkeys, at whose head Pope has placed Newton.”55 Man ceased to be a monkey only when he invented specific sounds as convenient expressions for specific ideas; he became man through language.56

Did La Mettrie admit a God as Prime Mover of the world machine? Voltaire and Diderot had defended the argument from design; La Mettrie rejected it scornfully:

All reasoning based on final causes is frivolous.… Nature makes silk the way the Bourgeois Gentilhomme speaks prose—without knowing it. It is as blind when it gives life as it is innocent when it destroys it.… Having, without seeing, made eyes that see, it has made, without thinking, a machine that thinks.57

La Mettrie was not explicitly an atheist; he affected rather to discard the question of God as unimportant; “it does not matter, for our peace of mind, whether matter is eternal or has been created, whether there is or is not a God.”58 But he quoted a probably fictitious “friend” as holding that “the universe will never be happy unless it is atheistic”; for then there will be no more theological disputes, no ecclesiastical persecutions, no more religious wars, and man will express his natural instincts with no sense of sin.59As for himself, La Mettrie was content with materialism. He ended his L’Homme machine on a defiant note: “Such is my system—or rather the truth, unless I am much deceived. It is short and simple. Dispute it now who will.”60 Perhaps as a parting jest he dedicated his agnostic manifesto to the pious poet and physiologist Albrecht von Haller, who rejected the dedication with horror in a letter to the Journal des savants for May, 1749:

The anonymous author of L’Homme machine having dedicated to me a work as dangerous as it is unusual, I feel that I owe it to God, to religion, and to myself to make the following statement: … I declare that the book in question is completely alien to my sentiments. I regard its dedication to myself as an outrage, exceeding in cruelty all those which its anonymous author has inflicted on so many worthy people; and I beg the … public to be assured that I have never had anything to do with the author, … that I do not know him, … and that I should look upon any consonance of views between us as one of the most unmitigated calamities that could possibly befall me.61

La Mettrie continued to print the dedication in later editions of his book.

L’Homme machine was widely reviewed and unanimously refuted. It was a simple matter to criticize the disorderly composition of the little volume, to condemn its self-assurance, and to expose careless errors of fact. It was not at all obvious that “the soul and the body fall asleep together”;62 some authors are more brilliant in their dreams than on the page. A sick body may house a good mind, as with Pope and Scarron; and our rare-meat lovers will not admit that they are still in the hunting stage. La Mettrie himself, who was up to every prank, published a pretended critique of his book in an anonymous L’Homme plus qu’une machine (Man More Than a Machine)—probably as a means of drawing attention to his major work.

On the other hand, he may have been really impressed by antimechanistic arguments. We know that he was interested in Trembley’s demonstration (1744) of the fresh-water polyp’s regenerative powers, which did not easily accord with mechanistic theory. Georg Stahl, of phlogiston fame, had boldly inverted the physiological thesis by declaring (1707) that instead of the body determining the ideas and volitions of the soul, it was the soul—the inherent animating principle—that determined the growth and action of the organs. Théophile de Bordeu—physician to d’Alembert—held that physiological processes, even of the simplest digestion, are incapable of mechanistic or purely chemical explanations.63 And Jean Baptiste Robinet offered a cosmic vitalism that endowed all matter with life and sensitivity. La Mettrie was apparently willing to accept this solution of the problem of matter versus life.

Meanwhile he proceeded to deduce a hedonistic ethic from his materialistic philosophy. In three separate works—Discours sur le bonheur, La Volupté (Pleasure), and L’ Art de jouir (The Art of Enjoyment)—he proclaimed self-love to be the highest virtue, and sense pleasure the supreme good. He resented the theological denigration of the pleasures of life, and questioned the alleged superiority of intellectual pleasure; all pleasures, he thought, are really sensual; hence simple people, who do not bother with intellect, are happier than philosophers. Let no man (said La Mettrie) repent his indulgence in sensual delights if these involved no harm to others. Nor should the criminal be held morally responsible for his crimes; he is the product of heredity and environment, over which he had no control. He should be treated not with sermons but with medicine; with a firmness that protects society, but also with a humaneness that recognizes universal determinism. “It would be desirable to have for judges none but the most skillful physicians.”64

These pronouncements marked the victory of Epicurus (misunderstood) over Zeno in eighteenth-century France: the Stoic philosophy of the classic age of Louis XIV surrendered, in the Enlightenment, to the Epicurean vindication of pleasure, the universalization of matter, and the banishment of the gods. No wonder La Mettrie’s books were widely sold to a public disillusioned of theology and tired of classic formalism and moral restraint. Polite society, however, shied away from him as an intellectual maverick who had incontinently revealed too many upper-class tenets. The clergy attacked him as an emissary of Satan; the theologians of Leiden prodded the Dutch government into ordering him out of the country. The free-thinking Frederick the Great invited him to Prussia (February, 1748), gave him a pension, and enrolled him in the Berlin Academy of Sciences. La Mettrie resumed the practice of medicine, and wrote, on asthma and dysentery, treatises that the King considered the best of their kind. Voltaire, after rubbing elbows with La Mettrie at Frederick’s court, wrote to Mme. Denis (November 6, 1750):

There is here too gay a man; it is La Mettrie. His ideas are fireworks always in the form of skyrockets. His chatter is amusing for half a quarter of an hour, and mortally tiresome thereafter. He has just made, without knowing it, a bad book, … in which he proscribes virtue and remorse, eulogizes the vices, and invites his readers to disorderly living—all without bad intention. There are in his work a thousand brilliant touches, and not half a page of reason; they are like flashes of lightning in the night.… God keep me from taking him for my doctor! He would give me corrosive sublimate instead of rhubarb, very innocently, and then begin to laugh. This strange doctor is the King’s reader, and the best of it is that he is at present reading to him the History of the Church. He goes over hundreds of pages of it, and there are places where monarch and reader are ready to choke with laughter.65

La Mettrie had described death as the conclusion of a farce (“la farce est jouée”); on November 11, 1751, aged forty-two, he offered himself as an example. At a dinner given by a patient whom he had cured of a serious ailment, he gorged himself with a pâte of pheasant, was seized with a violent fever, and died. For once, said Voltaire, the patient had killed his doctor.66 The King wrote for the funeral a handsome eulogy, and Voltaire breathed relief. The dead man’s ideas passed down to Diderot and d’Holbach, and entered into the spirit of the age.


I. Guillaume François Berthier, the brilliant Jesuit who edited the Journal de Trévoux, noted in the issue of July, 1759: “The custom has been established to call philosophe those who attack revealed religion, and ’persecutor’ those who battle for its defense.”1

II. The manuscript is in the Bibliothèque Nationale.

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