A. GERMAN IDEALISM IN GENERAL
Philosophy in the eighteenth century was dominated by the British empiricists, of whom Locke, Berkeley, and Hume may be taken as the representatives. In these men there was a conflict, of which they themselves appear to have been unaware, between their temper of mind and the tendency of their theoretical doctrines. In their temper of mind they were socially minded citizens, by no means self-assertive, not unduly anxious for power, and in favour of a tolerant world where, within the limits of the criminal law, every man could do as he pleased. They were good-natured, men of the world, urbane and kindly.
But while their temper was social, their theoretical philosophy led to subjectivism. This was not a new tendency; it had existed in late antiquity, most emphatically in St Augustine; it was revived in modern times by Descartes's cogito, and reached a momentary culmination in Leibniz's windowless monads. Leibniz believed that everything in his experience would be unchanged if the rest of the world were annihilated; nevertheless he devoted himself to the reunion of the Catholic and Protestant Churches. A similar inconsistency appears in Locke, Berkeley, and Hume.
In Locke, the inconsistency is still in the theory. We saw in an earlier chapter that Locke says, on the one hand: 'Since the mind, in all its thoughts and reasonings, hath no other immediate object but its own ideas, which it alone does or can contemplate, it is evident that our knowledge is only conversant about them.' And: 'Knowledge is the perception of the agreement or disagreement of two ideas.' Nevertheless, he maintains that we have three kinds of knowledge of real existence: intuitive, of our own; demonstrative, of God's; and sensitive, of things present to sense. Simpleideas, he maintains, are 'the product of things operating on the mind in a natural way'. How he knows this, he does not explain; it certainly goes beyond 'the agreement or disagreement of two ideas'.
Berkeley took an important step towards ending this inconsistency. For him, there are only minds and their ideas; the physical external world is abolished. But he still failed to grasp all the consequences of the epistemological principles that he took over from Locke. If he had been completely consistent, he would have denied knowledge of God and of all minds except his own. From such denial he was held back by his feelings as a clergyman and as a social being.
Hume shrank from nothing in pursuit of theoretical consistency, but felt no impulse to make his practice conform to his theory. Hume denied the Self, and threw doubt on induction and causation. He accepted Berkeley's abolition of matter, but not the substitute that Berkeley offered in the form of God's ideas. It is true that, like Locke, he admitted no simple idea without an antecedent impression, and no doubt he imagined an 'impression' as a state of mind directly caused by something external to the mind. But he could not admit this as a definition of 'impression', since he questioned the notion of 'cause'. I doubt whether either he or his disciples were ever clearly aware of this problem as to impressions. Obviously, on his view, an 'impression' would have to be defined by some intrinsic character distinguishing it from an 'idea', since it could not be defined causally. He could not therefore argue that impressions give knowledge of things external to ourselves, as had been done by Locke, and, in a modified form, by Berkeley. He should, therefore, have believed himself shut up in a solipsistic world, and ignorant of everything except his own mental states and their relations.
Hume, by his consistency, showed that empiricism, carried to its logical conclusion, led to results which few human beings could bring themselves to accept, and abolished, over the whole field of science, the distinction between rational belief and credulity. Locke had foreseen this danger. He puts into the mouth of a supposed critic the argument: 'If knowledge consists in agreement of ideas, the enthusiast and the sober man are on a level.' Locke, living at a time when men had grown tired of 'enthusiasm', found no difficulty in persuading men of the validity of his reply to this criticism. Rousseau, coming at a moment when people were, in turn, getting tired of reason, revived 'enthusiasm', and, accepting the bankruptcy of reason, allowed the heart to decide questions which the head left doubtful. From 1750 to 1794, the heart spoke louder and louder; at last Thermidor put an end, for a time, to its ferocious pronouncements, so far at least as France was concerned. Under Napoleon, heart and head were alike silenced.
In Germany, the reaction against Hume's agnosticism took a form far more profound and subtle than that which Rousseau had given to it. Kant, Fichte, and Hegel developed a new kind of philosophy, intended to safeguard both knowledge and virtue from the subversive doctrines of the late eighteenth century. In Kant, and still more in Fichte, the subjectivist tendency that begins with Descartes was carried to new extremes; in this respect there was at first no reaction against Hume. As regards subjectivism, the reaction began with Hegel, who sought, through his logic, to establish a new way of escape from the individual into the world.
The whole of German idealism has affinities with the romantic movement. These are obvious in Fichte, and still more so in Schelling; they are least so in Hegel.
Kant, the founder of German idealism, is not himself politically important, though he wrote some interesting essays on political subjects. Fichte and Hegel, on the other hand, both set forth political doctrines which had, and still have, a profound influence upon the course of history. Neither can be understood without a previous study of Kant, whom we shall consider in this chapter.
There are certain common characteristics of the German idealists, which can be mentioned before embarking upon detail.
The critique of knowledge, as a means of reaching philosophical conclusions, is emphasized by Kant and accepted by his followers. There is an emphasis upon mind as opposed to matter, which leads in the end to the assertion that only mind exists. There is a vehement rejection of utilitarian ethics in favour of systems which are held to be demonstrated by abstract philosophical arguments. There is a scholastic tone which is absent in the earlier French and English philosophers; Kant, Fichte, and Hegel were university professors, addressing learned audiences, not gentlemen of leisure addressing amateurs. Although their effects were in part revolutionary, they themselves were not intentionally subversive; Fichte and Hegel were very definitely concerned in the defence of the State. The lives of all of them were exemplary and academic; their views on moral questions were strictly orthodox. They made innovations in theology, but they did so in the interests of religion.
With these preliminary remarks, let us turn to the study of Kant.
B. OUTLINE OF KANT'S PHILOSOPHY
Immanuel Kant (1724–1804) is generally considered the greatest of modern philosophers. I cannot myself agree with this estimate, but it would be foolish not to recognize his great importance.
Throughout his whole life, Kant lived in or near Königsberg, in East Prussia. His outer life was academic and wholly uneventful, although he lived through the Seven Years' War (during part of which the Russians occupied East Prussia), the French Revolution, and the early part of Napoleon's career. He was educated in the Wolfian version of Leibniz's philosophy, but was led to abandon it by two influences: Rousseau and Hume. Hume, by his criticism of the concept of causality, awakened him from his dogmatic slumbers so at least he says, but the awakening was only temporary, and he soon invented a soporific which enabled him to sleep again. Hume, for Kant, was an adversary to be refuted, but the influence of Rousseau was more profound. Kant was a man of such regular habits that people used to set their watches by him as he passed their doors on his constitutional, but on one occasion his time-table was disrupted for several days; this was when he was reading Emile. He said that he had to read Rousseau's books several times, because, at a first reading, the beauty of the style prevented him from noticing the matter. Although he had been brought up as a pietist, he was a Liberal both in politics and in theology; he sympathized with the French Revolution until the Reign of Terror, and was a believer in democracy. His philosophy, as we shall see, allowed an appeal to the heart against the cold dictates of theoretical reason, which might, with a little exaggeration, be regarded as a pedantic version of the Savoyard Vicar. His principle that every man is to be regarded as an end in himself is a form of the doctrine of the Rights of Man; and his love of freedom is shown in his saying (about children as well as adults) that 'there can be nothing more dreadful than that the actions of a man should be subject to the will of another'.
Kant's early works are more concerned with science than with philosophy. After the earthquake of Lisbon he wrote on the theory of earthquakes; he wrote a treatise on wind, and a short essay on the question whether the west wind in Europe is moist because it has crossed the Atlantic Ocean. Physical geography was a subject in which he took great interest.
The most important of his scientific writings is his General Natural History and Theory of the Heavens (1755), which anticipates Laplace's nebular hypothesis, and sets forth a possible origin of the solar system. Parts of this work have a remarkable Miltonic sublimity. It has the merit of inventing what proved a fruitful hypothesis, but it does not, as Laplace did, advance serious arguments in its favour. In parts it is purely fanciful, for instance in the doctrine that all planets are inhabited, and that the most distant planets have the best inhabitants—a view to be praised for its terrestrial modesty, but not supported by any scientific grounds.
At a time when he was more troubled by the arguments of sceptics than he was earlier or later, he wrote a curious work called Dreams of a Ghost-seer, Illustrated by the Dreams of Metaphysics (1766). The 'ghost-seer' is Swedenborg, whose mystical system had been presented to the world in an enormous work of which four copies were sold, three to unknown purchasers and one to Kant. Kant, half serious and half in jest, suggests that Swedenborg's system, which he calls 'fantastic', is perhaps no more so than orthodox metaphysics. He is not, however, wholly contemptuous of Swedenborg. His mystical side, which existed though it did not much appear in his writings, admired Swedenborg, whom he calls 'very sublime'.
Like everybody else at that time, he wrote a treatise on the sublime and the beautiful. Night is sublime, day is beautiful; the sea is sublime, the land is beautiful; man is sublime, woman is beautiful; and so on.
The Encyclopaedia Britannica remarks that 'as he never married, he kept the habits of his studious youth to old age'. I wonder whether the author of this article was a bachelor or a married man.
Kant's most important book is The Critique of Pure Reason (first edition, 1781; second edition, 1787). The purpose of this work is to prove that, although none of our knowledge can transcend experience, it is, nevertheless, in part a priori and not inferred inductively from experience. The part of our knowledge which is a priori embraces, according to him, not only logic, but much that cannot be included in logic or deduced from it. He separates two distinctions which, in Leibniz, are confounded. On the one hand there is the distinction between 'analytic' and 'synthetic' propositions; on the other hand, the distinction between 'a priori' and 'empirical' propositions. Something must be said about each of these distinctions.
An 'analytic' proposition is one in which the predicate is part of the subject; for instance, 'a tall man is a man', or 'an equilateral triangle is a triangle'. Such propositions follow from the law of contradiction; to maintain that a tall man is not a man would be self-contradictory. A 'synthetic' proposition is one that is not analytic. All the propositions that we know only through experience are synthetic. We cannot, by a mere analysis of concepts, discover such truths as 'Tuesday was a wet day' or 'Napoleon was a great general'. But Kant, unlike Leibniz and all other previous philosophers, will not admit the converse, that all synthetic propositions are only known through experience. This brings us to the second of the above distinctions.
An 'empirical' proposition is one which we cannot know except by the help of sense-perception, either our own or that of someone else whose testimony we accept. The facts of history and geography are of this sort; so are the laws of science, whenever our knowledge of their truth depends on observational data. An 'a priori' proposition, on the other hand, is one which, though it may be elicited by experience, is seen, when known, to have a basis other than experience. A child learning arithmetic may be helped by experiencing two marbles and two other marbles, and observing that altogether he is experiencing four marbles. But when he has grasped the general proposition 'two and two are four' he no longer requires confirmation by instances; the proposition has a certainty which induction can never give to a general law. All the propositions of pure mathematics are in this sense a priori.
Hume had proved that the law of causality is not analytic, and had inferred that we could not be certain of its truth. Kant accepted the view that it is synthetic, but nevertheless maintained that it is known a priori. He maintained that arithmetic and geometry are synthetic, but are likewise a priori. He was thus led to formulate his problem in these terms:
How are synthetic judgments a priori possible?
The answer to this question, with its consequences, constitutes the main theme of The Critique of Pure Reason.
Kant's solution of the problem was one in which he felt great confidence. He had spent twelve years in looking for it, but took only a few months to write his whole long book after his theory had taken shape. In the preface to the first edition he says: 'I venture to assert that there is not a single metaphysical problem which has not been solved, or for the solution of which the key at least has not been supplied.' In the preface to the second edition he compares himself to Copernicus, and says that he has effected a Copernican revolution in philosophy.
According to Kant, the outer world causes only the matter of sensation, but our own mental apparatus orders this matter in space and time, and supplies the concepts by means of which we understand experience. Things in themselves, which are the causes of our sensations, are unknowable; they are not in space or time, they are not substances, nor can they be described by any of those other general concepts which Kant calls 'categories'. Space and time are subjective, they are part of our apparatus of perception. But just because of this, we can be sure that whatever we experience will exhibit the characteristics dealt with by geometry and the science of time. If you always wore blue spectacles, you could be sure of seeing everything blue (this is not Kant's illustration). Similarly, since you always wear spatial spectacles in your mind, you are sure of always seeing everything in space. Thus geometry is a priori in the sense that it must be true of everything experienced, but we have no reason to suppose that anything analogous is true of things in themselves, which we do not experience.
Space and time, Kant says, are not concepts; they are forms of 'intuition'. (The German word is 'Anschauung', which means literally 'looking at' or 'view'. The word 'intuition', though the accepted translation, is not altogether a satisfactory one.) There are also, however, a priori concepts; these are the twelve 'categories', which Kant derives from the forms of the syllogism. The twelve categories are divided into four sets of three: (1) of quantity: unity, plurality, totality; (2) of quality: reality, negation, limitation; (3) of relation: substance-and-accident, cause-and-effect, reciprocity; (4) of modality: possibility, existence, necessity. These are subjective in the same sense in which space and time are—that is to say, our mental constitution is such that they are applicable to whatever we experience, but there is no reason to suppose them applicable to things in themselves. As regards cause, however, there is an inconsistency, for things in themselves are regarded by Kant as causes of sensations, and free volitions are held by him to be causes of occurrences in space and time. This inconsistency is not an accidental oversight; it is an essential part of his system.
A large part of The Critique of Pure Reason is occupied in showing the fallacies that arise from applying space and time or the categories to things that are not experienced. When this is done, so Kant maintains, we find ourselves troubled by 'antinomies'—that is to say, by mutually contradictory propositions each of which can apparently be proved. Kant gives four such antinomies, each consisting of thesis and antithesis.
In the first, the thesis says: 'The world has a beginning in time, and is also limited as regards space.' The antithesis says: 'The world has no beginning in time, and no limits in space; it is infinite as regards both time and space.'
The second antinomy proves that every composite substance both is, and is not, made up of simple parts.
The thesis of the third antinomy maintains that there are two kinds of causality, one according to the laws of nature, the other that of freedom; the antithesis maintains that there is only causality according to the laws of nature.
The fourth antinomy proves that there is, and is not, an absolutely necessary Being.
This part of the Critique greatly influenced Hegel, whose dialectic proceeds wholly by way of antinomies.
In a famous section, Kant sets to work to demolish all the purely intellectual proofs of the existence of God. He makes it clear that he has other reasons for believing in God; these he was to set forth later in The Critique of Practical Reason. But for the time being his purpose is purely negative.
There are, he says, only three proofs of God's existence by pure reason; these are the ontological proof, the cosmological proof, and the physicotheological proof.
The ontological proof, as he sets it forth, defines God as the ens realissimum, the most real being; i.e. the subject of all predicates that belong to being absolutely. It is contended, by those who believe the proof valid, that, since 'existence' is such a predicate, this subject must have the predicate 'existence', i.e. must exist. Kant objects that existence is not a predicate. A hundred thalers that I merely imagine may, he says, have all the same predicates as a hundred real thalers.
The cosmological proof says: If anything exists, then an absolutely necessary Being must exist; now I know that I exist; therefore an absolutely necessary Being exists, and this must be the ens realissimum. Kant maintains that the last step in this argument is the ontological argument over again, and that it is therefore refuted by what has been already said.
The physico-theological proof is the familiar argument from design, but in a metaphysical dress. It maintains that the universe exhibits an order which is evidence of purpose. This argument is treated by Kant with respect, but he points out that, at best, it proves only an Architect, not a Creator, and therefore cannot give an adequate conception of God. He concludes that 'the only theology of reason which is possible is that which is based upon moral laws or seeks guidance from them'.
God, freedom, and immortality, he says, are the three 'ideas of reason'. But although pure reason leads us to form these ideas, it cannot itself prove their reality. The importance of these ideas is practical, i.e. connected with morals. The purely intellectual use of reason leads to fallacies; its only right use is directed to moral ends.
The practical use of reason is developed briefly near the end of The Critique of Pure Reason, and more fully in The Critique of Practical Reason (1786). The argument is that the moral law demands justice, i.e. happiness proportional to virtue. Only Providence can insure this, and has evidently not insured it in this life. Therefore there is a God and a future life; and there must be freedom, since otherwise there would be no such thing as virtue.
Kant's ethical system, as set forth in his Metaphysic of Morals (1785), has considerable historical importance. This book contains the 'categorical imperative', which, at least as a phrase, is familiar outside the circle of professional philosophers. As might be expected, Kant will have nothing to do with utilitarianism, or with any doctrine which gives to morality a purpose outside itself. He wants, he says, 'a completely isolated metaphysic of morals, which is not mixed with any theology or physics or hyperphysics'. All moral concepts, he continues, have their seat and origin wholly a priori in the reason. Moral worth exists only when a man acts from a sense of duty; it is not enough that the act should be such as duty might have prescribed. The tradesman who is honest from self-interest, or the man who is kind from benevolent impulse, is not virtuous. The essence of morality is to be derived from the concept of law; for, though everything in nature acts according to laws, only a rational being has the power of acting according to the idea of law; i.e. by Will. The idea of an objective principle in so far as it is compelling to the will, is called a command of the reason, and the formula of the command is called an imperative.
There are two sorts of imperative: the hypothetical imperative which says 'You must do so-and-so if you wish to achieve such-and-such an end'; and the categorical imperative, which says that a certain kind of action is objectively necessary, without regard to any end. The categorical imperative is synthetic and a priori. Its character is deduced by Kant from the concept of Law:
'If I think of a categorical imperative, I know at once what it contains. For as the imperative contains, besides the Law, only the necessity of the maxim to be in accordance with this law, but the Law contains no condition by which it is limited, nothing remains over but the generality of a law in general, to which the maxim of the action is to be conformable, and which conforming alone presents the imperative as necessary. Therefore the categorical imperative is a single one, and in fact this: Act only according to a maxim by which you can at the same time will that it shall become a general law.' Or: 'Act as if the maxim of your action were to become through your will a general natural law.'
Kant gives as an illustration of the working of the categorical imperative that it is wrong to borrow money, because if we all tried to do so there would be no money left to borrow. One can in like manner show that theft and murder are condemned by the categorical imperative. But there are some acts which Kant would certainly think wrong but which cannot be shown to be wrong by his principles, for instance suicide; it would be quite possible for a melancholic to wish that everybody should commit suicide. His maxim seems, in fact, to give a necessary but not a sufficient criterion of virtue. To get a sufficient criterion, we should have to abandon Kant's purely formal point of view, and take some account of the effects of actions. Kant, however, states emphatically that virtue does not depend upon the intended result of an action, but only on the principle of which it is itself a result; and if this is conceded, nothing more concrete than his maxim is possible.
Kant maintains, although his principle does not seem to entail this consequence, that we ought so to act as to treat every man as an end in himself. This may be regarded as an abstract form of the doctrine of the rights of man, and it is open to the same objections. If taken seriously, it would make it impossible to reach a decision whenever two people's interests conflict. The difficulties are particularly obvious in political philosophy, which requires some principle, such as preference for the majority, by which the interests of some can, when necessary, be sacrificed to those of others. If there is to be any ethic of government, the end of government must be one, and the only single end compatible with justice is the good of the community. It is possible, however, to interpret Kant's principle as meaning, not that each man is an absolute end, but that all men should count equally in determining actions by which many are affected. So interpreted, the principle may be regarded as giving an ethical basis for democracy. In this interpretation, it is not open to the above objection.
Kant's vigour and freshness of mind in old age are shown by his treatise on Perpetual Peace (1795). In this work he advocates a federation of free States, bound together by a covenant forbidding war. Reason, he says, utterly condemns war, which only an international government can prevent. The civil constitution of the component States should, he says, be 'republican', but he defines this word as meaning that the executive and the legislative are separated. He does not mean that there should be no king; in fact, he says that it is easiest to get a perfect government under a monarchy. Writing under the impact of the Reign of Terror, he is suspicious of democracy; he says that it is of necessity despotism, since it establishes an executive power. 'The "whole people", so-called, who carry their measures are really not all, but only a majority: so that here the universal will is in contradiction with itself and with the principle of freedom.' The phrasing shows the influence of Rousseau, but the important idea of a world federation as the way to secure peace is not derived from Rousseau.
Since 1933, this treatise has caused Kant to fall into disfavour in his own country.
C. KANT'S THEORY OF SPACE AND TIME
The most important part of The Critique of Pure Reason is the doctrine of space and time. In this section I propose to make a critical examination of this doctrine.
To explain Kant's theory of space and time clearly is not easy, because the theory itself is not clear. It is set forth both in The Critique of Pure Reason and in the Prolegomena; the latter exposition is the easier, but is less full than that in the Critique. I will try first to expound the theory, making it as plausible as I can; only after exposition will I attempt criticism.
Kant holds that the immediate objects of perception are due partly to external things and partly to our own perceptive apparatus. Locke had accustomed the world to the idea that the secondary qualities—colours, sounds, smells, etc.—are subjective, and do not belong to the object as it is in itself. Kant, like Berkeley and Hume, though in not quite the same way, goes further, and makes the primary qualities also subjective. Kant does not at most times question that our sensations have causes, which he calls 'things-in-themselves' or 'noumena'. What appears to us in perception, which he calls a 'phenomenon', consists of two parts: that due to the object, which he calls the 'sensation', and that due to our subjective apparatus, which, he says, causes the manifold to be ordered in certain relations. This latter part he calls the form of the phenomenon. This part is not itself sensation, and therefore not dependent upon the accident of environment; it is always the same, since we carry it about with us, and it is a priori in the sense that it is not dependent upon experience. A pure form of sensibility is called a 'pure intuition' (Anschauung); there are two such forms, namely space and time, one for the outer sense, one for the inner.
To prove that space and time are a priori forms, Kant has two classes of arguments, one metaphysical, the other epistemological, or, as he calls it, transcendental. The former class of arguments are taken directly from the nature of space and time, the latter indirectly from the possibility of pure mathematics. The arguments about space are given more fully than those about time, because it is thought that the latter are essentially the same as the former.
As regards space, the metaphysical arguments are four in number.
(1) Space is not an empirical concept, abstracted from outer experiences, for space is presupposed in referring sensations to something external, and external experience is only possible through the presentation of space.
(2) Space is a necessary presentation a priori, which underlies all external perceptions; for we cannot imagine that there should be no space, although we can imagine that there should be nothing in space.
(3) Space is not a discursive or general concept of the relations of things in general, for there is only one space, of which what we call 'spaces' are parts, not instances.
(4) Space is presented as an infinite given magnitude, which holds within itself all the parts of space; this relation is different from that of a concept to its instances, and therefore space is not a concept but an Anschauung.
The transcendental argument concerning space is derived from geometry. Kant holds that Euclidean geometry is known a priori, although it is synthetic, i.e. not deducible from logic alone. Geometrical proofs, he considers, depend upon the figures; we can see, for instance, that, given two intersecting straight lines at right angles to each other, only one straight line at right angles to both can be drawn through their point of intersection. This knowledge, he thinks, is not derived from experience. But the only way in which my intuition can anticipate what will be found in the object is if it contains only the form of my sensibility, antedating in my subjectivity all the actual impressions. The objects of sense must obey geometry, because geometry is concerned with our ways of perceiving, and therefore we cannot perceive otherwise. This explains why geometry, though synthetic, is a priori and apodeictic.
The arguments with regard to time are essentially the same, except that arithmetic replaces geometry with the contention that counting takes time.
Let us now examine these arguments one by one.
The first of the metaphysical arguments concerning space says: 'Space is not an empirical concept abstracted from external experiences. For in order that certain sensations may be referred to something outside me [i.e. to something in a different position in space from that in which I find myself], and further in order that I may be able to perceive them as outside and beside each other, and thus as not merely different, but in different places, the presentation of space must already give the foundation [zum Grunde liegen].' Therefore external experience is only possible through the presentation of space.
The phrase 'outside me [i.e. in a different place from that in which I find myself]' is a difficult one. As a thing-in-itself, I am not anywhere, and nothing is spatially outside me; it is only my body as a phenomenon that can be meant. Thus all that is really involved is what comes in the second part of the sentence, namely that I perceive different objects as in different places. The image which arises in one's mind is that of a cloak-room attendant who hangs different coats on different pegs; the pegs must already exist, but the attendant's subjectivity arranges the coats.
There is here, as throughout Kant's theory of the subjectivity of space and time, a difficulty which he seems to have never felt. What induces me to arrange objects of perception as I do rather than otherwise? Why, for instance, do I always see people's eyes above their mouths and not below them? According to Kant, the eyes and the mouth exist as things in themselves, and cause my separate percepts, but nothing in them corresponds to the spatial arrangement that exists in my perception. Contrast with this the physical theory of colours. We do not suppose that in matter there are colours in the sense in which our percepts have colours, but we do think that different colours correspond to different wave-lengths. Since waves, however, involve space and time, there cannot, for Kant, be waves in the causes of our percepts. If, on the other hand, the space and time of our percepts have counterparts in the world of matter, as physics assumes, then geometry is applicable to these counterparts, and Kant's arguments fail. Kant holds that the mind orders the raw material of sensation, but never thinks it necessary to say why it orders it as it does and not otherwise.
In regard to time this difficulty is even greater, because of the intrusion of causality. I perceive the lightning before I perceive the thunder; a thing-in-itself A caused my perception of lightning, and another thing-in-itself B caused my perception of thunder, but A was not earlier than B, since time exists only in the relations of percepts. Why, then, do the two timeless things A and B produce effects at different times? This must be wholly arbitrary if Kant is right, and there must be no relation between A and B corresponding to the fact that the percept caused by A is earlier than that caused by B.
The second metaphysical argument maintains that it is possible to imagine nothing in space, but impossible to imagine no space. It seems to me that no serious argument can be based upon what we can or cannot imagine; but I should emphatically deny that we can imagine space with nothing in it. You can imagine looking at the sky on a dark cloudy night, but then you yourself are in space, and you imagine the clouds that you cannot see. Kant's space, as Vaihinger pointed out, is absolute, like Newton's, and not merely a system of relations. But I do not see how absolute empty space can be imagined.
The third metaphysical argument says: 'Space is not a discursive, or, as is said, general concept of the relations of things in general, but a pure intu ition. For, in the first place, we can only imagine [sich vorstellen] one single space, and if we speak of 'spaces' we mean only parts of one and the same unique space. And these parts cannot precede the whole as its parts … but can only be thought as in it. It [space] is essentially unique, the manifold in it rests solely on limitations.' From this it is concluded that space, is an a priori intuition.
The gist of this argument is the denial of plurality in space itself.
What we call 'spaces' are neither instances of a general concept 'a space', nor parts of an aggregate. I do not know quite what, according to Kant, their logical status is, but in any case they are logically subsequent to space. To those who take, as practically all moderns do, a relational view of space, this argument becomes incapable of being stated, since neither 'space' nor 'spaces' can survive as a substantive.
The fourth metaphysical argument is chiefly concerned to prove that space is an intuition, not a concept. Its premiss is 'space is imagined [or presented, vorgestellt] as an infinite given magnitude'. This is the view of a person living in a flat country, like that of Königsberg; I do not see how an inhabitant of an Alpine valley could adopt it. It is difficult to see how anything infinite can be 'given'. I should have thought it obvious that the part of space that is given is that which is peopled by objects of perception, and that for other parts we have only a feeling of possibility of motion. And if so vulgar an argument may be intruded, modern astronomers maintain that space is in fact not infinite, but goes round and round, like the surface of the globe.
The transcendental (or epistemological) argument, which is best stated in the Prolegomena, is more definite than the metaphysical arguments, and is also more definitely refutable. 'Geometry', as we now know, is a name covering two different studies. On the one hand, there is pure geometry, which deduces consequences from axioms, without inquiring whether the axioms are 'true'; this contains nothing that does not follow from logic, and is not 'synthetic', and has no need of figures such as are used in geometrical textbooks. On the other hand, there is geometry as a branch of physics, as it appears, for example, in the general theory of relativity; this is an empirical science, in which the axioms are inferred from measurements, and are found to differ from Euclid's. Thus of the two kinds of geometry one is a priori but not synthetic, while the other is synthetic but not a priori. This disposes of the transcendental argument.
Let us now try to consider the questions raised by Kant as regards space in a more general way. If we adopt the view, which is taken for granted in physics, that our percepts have external causes which are (in some sense) material, we are led to the conclusion that all the actual qualities in percepts are different from those in their unperceived causes, but that there is a certain structural similarity between the system of percepts and the system of their causes. There is, for example, a correlation between colours (as perceived) and wave-lengths (as inferred by physicists). Similarly there must be a correlation between space as an ingredient in percepts and space as an ingredient in the system of unperceived causes of percepts. All this rests upon the maxim 'same cause, same effect', with its obverse, 'different effects, different causes'. Thus, e.g. when a visual percept A appears to the left of a visual percept B, we shall suppose that there is some corresponding relation between the cause of A and the cause of B.
We have, on this view, two spaces, one subjective and one objective, one known in experience and the other merely inferred. But there is no difference in this respect between space and other aspects of perception, such as colours and sounds. All alike, in their subjective forms, are known empirically; all alike, in their objective forms, are inferred by means of a maxim as to causation. There is no reason whatever for regarding our knowledge of space as in any way different from our knowledge of colour and sound and smell.
With regard to time, the matter is different, since, if we adhere to the belief in unperceived causes of percepts, the objective time must be identical with the subjective time. If not, we get into the difficulties already considered in connection with lightning and thunder. Or take such a case as the following: You hear a man speak, you answer him, and he hears you. His speaking, and his hearing of your reply, are both, so far as you are concerned, in the unperceived world; and in that world the former precedes the latter. Moreover his speaking precedes your hearing in the objective world of physics; your hearing precedes your reply in the subjective world of percepts; and your reply precedes his hearing in the objective world of physics. It is clear that the relation 'precedes' must be the same in all these propositions. While, therefore, there is an important sense in which perceptual space is subjective, there is no sense in which perceptual time is subjective.
The above arguments assume, as Kant does, that percepts are caused by 'things in themselves', or, as we should say, by events in the world of physics. This assumption, however, is by no means logically necessary. If it is abandoned, percepts cease to be in any important sense 'subjective', since there is nothing with which to contrast them.
The 'thing-in-itself' was an awkward element in Kant's philosophy, and was abandoned by his immediate successors, who accordingly fell into something very like solipsism. Kant's inconsistencies were such as to make it inevitable that philosophers who were influenced by him should develop rapidly either in the empirical or in the absolutist direction; it was, in fact, in the latter direction that German philosophy moved until after the death of Hegel.
Kant's immediate successor, Fichte (1762–1814), abandoned 'things in themselves', and carried subjectivism to a point which seems almost to involve a kind of insanity. He holds that the Ego is the only ultimate reality, and that it exists because it posits itself; the non-Ego, which has a subordinate reality, also exists only because the Ego posits it. Fichte is not important as a pure philosopher, but as the theoretical founder of German nationalism, by his Addresses to the German Nation (1807–8), which were intended to rouse the Germans to resistance to Napoleon after the battle of Jena. The Ego as a metaphysical concept easily became confused with the empirical Fichte; since the Ego was German, it followed that the Germans were superior to all other nations. 'To have character and to be a German,' says Fichte, 'undoubtedly mean the same thing.' On this basis he worked out a whole philosophy of nationalistic totalitarianism, which had great influence in Germany.
His immediate successor Schelling (1775–1854) was more amiable but not less subjective. He was closely associated with the German romantics; philosophically, though famous in his day, he is not important. The important development from Kant's philosophy was that of Hegel.