Chapter I: Part 1

*THE PHILOSOPHY OF
IMMANUEL KANT*

BY A. D. LINDSAY, M.A.

FELLOW AND TUTOR OF BALLIOL COLLEGE, OXFORD

LONDON: T. C. & E. C. JACK, LTD.
35 PATERNOSTER ROW, E.C., & EDINBURGH
NEW YORK: DODGE PUBLISHING CO.

*FOREWORD*

There is a story that Schopenhauer used to begin his lectures on Kant by saying: "Let no one _tell_ you what is contained in the _Critique of Pure Reason_." The writer of this little book hopes that no one will imagine that he has disregarded this warning. There are no short-cuts to the understanding of a great philosopher, and the only way to appreciate the greatness of a philosophic system is to study the philosopher's own writings. All that the writer of a book like this can hope to do is to persuade others to undertake that study by interesting them in the problems with which it deals, and by offering a few suggestions which may help to an understanding of it. I have said nothing about the numerous other works which Kant wrote. For the three _Critiques_ contain his system, and the understanding of that is all-important.

*CONTENTS*

CHAP.

I. THE IDEA OF CRITICISM

II. KANT'S STATEMENT OF THE PROBLEM. SYNTHETIC A PRIORI JUDGMENTS

III. KANT'S IDEALISM. TIME AND SPACE

IV. THE CATEGORIES AND THE PRINCIPLES OF PURE UNDERSTANDING

V. THE ANTINOMIES AND CRITICISM OF THE PROOFS OF THE EXISTENCE OF GOD

VI. KANT'S MORAL THEORY

VII. THE "CRITIQUE OF JUDGMENT"

BIBLIOGRAPHY

*THE PHILOSOPHY OF KANT*

*CHAPTER I*

*THE IDEA OF CRITICISM*

"It is a difficult matter," says Heine, "to write the life history of Immanuel Kant, for he had neither life nor history. He lived a mechanically ordered, abstract, old bachelor kind of existence in a quiet, retired alley in Koenigsberg, an old town in the north-east corner of Germany." The times he lived in were stirring enough. He was born in 1724, and died in 1804. He lived through the Seven Years' War that first made Germany a nation, he followed with sympathy the United States War of Independence, he saw the French Revolution and the beginning of the career of Napoleon. Yet in all his long life he never moved out of the province in which he was born, and nothing was allowed to interrupt the steady course of his lecturing, studying, and writing. "Getting up," continues Heine, "drinking coffee, lecturing, eating, going for a walk, everything had its fixed time; and the neighbours knew that it must be exactly half-past four when Immanuel Kant, in his gray frock-coat, with his Spanish cane in his hand, stepped from his door and walked towards the little lime-tree avenue, which is called after him the Philosopher's Walk." "Strange contrast," reflects Heine, "between the man's outward life and his destructive, world-smashing thoughts." As the political history of the eighteenth century came to an end when the French Revolution spilled over the borders of France and drove Napoleon up and down Europe, breaking up the old political systems and inaugurating modern Europe, so its opposing currents of thought were gathered together in the mind of a weak-chested, half-invalid little man in Koenigsberg, and from their meeting a new era in philosophy began.

There are some philosophers to whom truth seems to come almost unsought, as an immediate authoritative vision. Kant was not one of these. His greatest work, the _Critique of Pure Reason_, was conceived when he was forty-eight, and published in 1781, when he was fifty-seven. It was the outcome of half a lifetime's patient study and thought. Heine says of him: "He was the perfect type of the small shopkeeper. Nature had meant him to weigh coffee and sugar, but fate willed that he should weigh other things and put a God on his scales, and his weighing was exact." The sneer is unjust, but there is something in the simile; for Kant's philosophy was a kind of taking stock, a survey of the great movement of thought from the time when the Renaissance and the Reformation made thought free, an attempt to estimate the achievements of the new sciences, to deal with their conflicting claims and ideals and say what it all came to. In Kant modern science, which began with Descartes and Galileo, first became conscious of itself.

This taking stock Kant called _Criticism_. His great books are all called Critiques--the _Critique of Pure Reason_, the _Critique of Practical Reason_, the _Critique of Judgment_. He called his philosophy the Critical Philosophy or Critical Idealism. Essential to an understanding of Kant is an understanding of what he meant by criticism, and why he opposes it to dogmatism and scepticism; for the necessity and possibility of such a criticism was his great philosophical discovery. We have called Kant's work a survey of the achievements of the thought of his times, but it was very much more than that, and has a much more universal significance than could belong to any history of the thought of one epoch. For these achievements of thought, though great, were conflicting and partial. They contrasted with failure and barrenness in other directions, and they seemed to be due to different methods. This success of thought in one direction and its failure in another, and this uncertainty about the true method of science, were problems which at once presented themselves to an impartial observer, and Kant held that they could be answered only by taking stock of actual attainments, and by criticism of the powers and range of human thought in general.

The problem that presented itself to him will be understood if we look for a moment at the history of thought in the seventeenth and eighteenth centuries. One thing that Kant noted in it was the steady and sure progress of physics. "With the experiments of Galileo and Torricelli," he says in the preface to the second edition of the first _Critique_, "a new light flashed on all students of nature." The continued success of physics meant the successful application of mathematics to the concrete world, and along with it a remarkable development of mathematics itself. This sudden success inspired men to feel that they had discovered a way of explaining the universe; they contrasted the fertility of their new methods with the barrenness of scholastic speculation in morals and theology; they felt confident that all that was wanted to the attainment of certain knowledge in all spheres of human interest was the extension of these methods. If men would only set to work the right way, they were sure that all difficulties would be overcome; and, by reflection upon their own success, they hoped to explain what the right way was.

Unfortunately this was not easy, for the advance from pure mathematics to physics, from a study of the nature of pure mathematical conceptions to an inquiry into the laws of falling bodies, implied a change whose nature was not clear to the men who had themselves made the advance. A conflict arose between those who thought more of the fact that knowledge, to be certain, must be capable of mathematical expression, and those who thought more of the basis of experiment and observation on which the new sciences depended, who remembered that these sciences began when Galileo, instead of thinking in the abstract how bodies ought to fall, dropped bodies of different weights from the top of the leaning tower of Pisa and observed what actually happened. Descartes was the great representative of the first school. He began by insisting on the difference between mathematical truth which could be, as he said, clearly and distinctly conceived, and ordinary opinion about things which was full of guesswork and imagination. Scientific knowledge was possible, he thought, only by apprehending the real or primary qualities of things which were mathematical, in contradistinction to their secondary qualities--their colour, smell, &c.--which were less real. Thence he came to think that the real world was mathematical in nature, like a huge, intricate geometrical figure. The elements of mere fact, in our present knowledge, its dependence on observation and experiment, he thought of as temporary defects which the progress of science would remove. What we ordinarily call perception, indeed, in the sense of awareness of things in time and space, was described by Descartes' successors as confused thinking. Our knowledge of the world would, it was hoped, become a vast mathematical system, all the detail and complexity of which would be rigorously deducible from a few central truths.

This general way of thinking was called Rationalism. Kant ordinarily calls it Dogmatism. It was attacked by other scientists for its view of the nature of space and time. No one who reflects at all can fail to distinguish a difference between the way in which we see the truth of a geometrical proposition--that, _e.g._, the three angles of a triangle are equal to two right angles--and the way in which we judge that such and such a figure drawn on a board is a triangle, or make judgments about the way in which things are actually arranged in space or succeed in time. Judgments of the latter kind involve words like "here" and "there," "now" and "then," words which are all a kind of pointing. It seems impossible from considering the nature of a triangle to deduce why any existing thing should be called triangular, and all statements about the position of things in space and time seem to be derived not from a consideration of the general nature of space and time, but from observation. Now the science which had made perhaps the most striking progress in the time we are speaking of, physical astronomy, involved any number of statements about the position of bodies in space. The Rationalist school admitted this, but held that that was due to the fact that science was not sufficiently thought out. In time, they hoped, all statements about position in space would disappear. To think of things in spatial order was to think confusedly. Newton, on the other hand, held that space could not be explained away, that astronomy implied an absolute space in which things existed, that the spatial relations of things could not be explained by the nature of the things themselves, but only by a reference to absolute space in which they all were. This meant that observation or perception was something of which you could not hope and should not wish to get rid, and that an ideal of knowledge in which all applied mathematics should have been transmuted into pure mathematics was a vain one. Astronomy implied both mere observation and apprehension of necessary relations. Here was a science which seemed to employ both methods together. Galileo, in fact could not have made his discovery without observation but men had observed bodies falling for ages without discovering the laws of motion. Further, the laws of motion, once discovered, made men in some degree independent of observation, made them able to say of actual concrete things not only what had happened, but what must happen.

Such difficulties as these arose from reflection on the aims and methods of the mathematical sciences, but there was much genuinely scientific inquiry in the seventeenth and eighteenth centuries, which showed no signs of taking mathematical form; chemistry and biology, for example, were still almost entirely empirical. Furthermore, thinkers were not concerned with science alone. These centuries saw a great revival of interest in speculation on human affairs, history, politics, morals and theology. England, which was the home of free discussion on questions of politics and morals, and where, more than in most other countries, there was free discussion on theology, became also the home of empiricism. The empirical movement, indeed, drew much of its impetus from a reaction against Hobbes, the only great English thinker who unhesitatingly applied the mechanical and deterministic assumptions of the new sciences to morals and politics, and arrived by this uncompromising method at results so obviously repellent that no man of any sense could accept them, and so consistently presented that they could not be refuted save by a refutation of the assumptions upon which they were founded. Such a refutation was, in fact, undertaken by Locke, the first great representative of the empirical school. He was interested alike in the more obviously empirical sciences of chemistry and biology, and in politics. He was not a very consistent or systematic thinker, but he had other gifts perhaps as valuable. He was a man of great common sense and breadth of view, and was able thereby to take a conspectus of the general situation in the various spheres of inquiry, to notice the obvious differences in our knowledge of mathematics, of chemical and biological fact, and of theology, and to see that these constituted a problem. We find in him the first statement of the necessity of philosophical criticism. It is contained in his account of the origin of the _Essay concerning Human Understanding_. "Were it fit to trouble thee with the history of this _Essay_, I should tell thee that five or six friends, meeting at my chamber, and discoursing on a subject very remote from this" (they were discussing the "principles of morality and revealed religion"), "found themselves quickly at a stand, by the difficulties that rose on every side. After we had awhile puzzled ourselves, without coming any nearer a resolution of those doubts which perplexed us, it came into my thoughts that we took a wrong course; and that, before we set ourselves upon inquiries of that nature, it was necessary to examine our own abilities, and see what _objects_ our understandings were, or were not, fitted to deal with."

We have here the same general starting point of inquiry as we shall afterwards find in Kant. There are certain, obstinate puzzles which we meet with in discussion which can only be solved by going back and inquiring into the nature of knowledge and the powers of our minds. Unfortunately, as Kant points out, Locke went the wrong way about his task. He describes it as "a plain historical inquiry." He thought that he had only to look into his mind and see what was in it, as he might open a door and look into a room. The result is that he thinks of all knowledge as consisting simply in looking at what is present to the mind. We can know, therefore, whatever can be present to the mind, and the limitations of knowledge are discovered by asking what can be so present to the mind. The conclusions to which he comes as to different spheres of human inquiry are roughly these: We can have knowledge of mathematics because there we are concerned only with ideas present to the mind, and with noting their agreement and disagreement. We can have no knowledge of such questions as the immortality of the soul, or the nature of spirits, for they are beyond our observation. As regards existing things, we can have knowledge of them, in so far as they are present to our minds, and no further. The meaning of "present to the mind" was never clearly analysed by Locke; but he meant, for example, that we can observe that an object which is yellow, and which we call gold, is also heavy, and can be dissolved by Aqua Regia, but we cannot say why that is so, and we ought not, on Locke's principles, to have any ground for supposing that these qualities will go on co-existing.

The element of truth in Locke's position is this. When we are examining concrete things like pieces of gold or any chemical substance, we find in them a number of varying qualities whose connection we cannot understand. We do not know why a metal of a certain specific gravity should also be yellow; we can only note the fact. Hence in chemistry our method must be quite different from the method of mathematics. In mathematics we start from the definition, and we can understand the connection of the properties of a geometrical figure, and see that they all follow necessarily from the definition. But in sciences like chemistry a definition does not take us any further; we can only find out the properties of a substance by observation and experiment. Locke explains this difference by saying that in the former case we are only concerned with agreement among our own ideas, in the second place we are concerned somehow with things outside us. This explanation will not stand. It is not true that mathematics is simply analysis of an arbitrary definition, as Locke seems to suggest. It involves construction, or, as Kant calls it, synthesis. It is a process of discovering new truths. Secondly, our statements about concrete objects are not statements of qualities we see co-existing at the moment. They are statements about all gold or all men; in other words, they are universal, and Locke found it impossible to explain the universality of such propositions--what we mean, _e.g._ when we talk about the nature of gold or of man, not of this gold or this man that I see before me. Lastly, this distinction of mathematics and the empirical sciences by a distinction of spheres does not allow, as we saw, for a science like astronomy, which builds on mathematics and yet applies to the concrete world.

These difficulties were seen more clearly by Hume, at once the greatest and the most thorough-going of empiricists. He cut the knot in regard to mathematics by asserting that geometry, just because it has clearly an application to the existing world, had no more certainty than any other empirical inquiry, while arithmetic and algebra, he agreed, were certain, but confined their application to the sphere of our own ideas. Both positions are almost obviously inconsistent with the facts. In considering the nature of our judgments about concrete existences he raised a more profound problem. All such judgments, as he said, imply the principle of causation, or of what is called, in modern times, the principle of the uniformity of nature. That principle we take with us in our investigation of the existing world. Yet, as Hume saw, we do not observe causes; we only observe succession and change. We seem, therefore, to put into the world we see a necessity and uniformity which the observed facts do not warrant. How is this to be explained?

Hume's answer is ingenious. The principle of causation cannot be rationally justified, and the necessary connection we predicate of changes in the outside world is not in the things; it is only a feeling in ourselves, and is the result of custom. After seeing the same succession several times, we come somehow to feel differently about it, and that feeling of difference we express by saying that we have before us an instance not of simple succession, but of cause and effect.

This is not the place to discuss the difficulties of Hume's position; it is enough to notice how entirely passive it makes the mind, and how alien such an explanation is from the spirit of inquiry and discovery. If cause is simply the effect of custom on the mind, then the facts either produce that effect or they do not. In neither case is there anything to find out. But the scientist, in investigating causes, however strongly he may hold that he has to observe the facts, knows also that he has a problem to solve, that he has to discover the right way to go about it, must adopt some principle in dealing with the facts. Pure passivity will help him little.

Hume's account of causation, then, is really a denial of even empirical science, and yet it helped to make clear an important truth; for, although we do not get the _principle_ of causation from experience, we have to go to experience to discover causal laws. We do not discover causation by analysing a cause and seeing that it is such that, from its nature, it must produce a certain effect. All knowledge of causation goes back to observed succession, though all cases of observed and even repeated succession are not cases of causation. Hume, therefore, was right in saying that where there could be no observed succession there could be no knowledge of causation.

Both the rationalistic and the empirical explanations of science had failed, the one because it could find no room for observation of facts, the other because it could find no room for principles governing that observation; and we shall see that Kant started with a consciousness of this double failure. He saw that Hume's criticism of causation raised problems for which the rationalist had no answer, and yet that the position reached by Hume was incompatible with the existence of science.

The same failure of both rationalism and empiricism had become evident in another sphere--that of morals and religion. The relation of philosophy to science is always twofold. Philosophy is partly concerned with analysing and reflecting on the methods of the different sciences, partly with seeking to adjust the rival and conflicting claims of the two great departments of man's life--science and religion.

It might seem, at first sight, as though in morals and religion rationalism were the only possible method to be approved by philosophy, for, inasmuch as morals are concerned with what ought to be, not with what is, they cannot depend on observation, but must be deduced from some principle above experience; nor are objects of religion, God and the soul, objects of observation. No man can "by searching find out God."

It was natural, therefore, that both on the Continent and in England morality and religion began by being rationalistic. Descartes believed that his mathematical method could be applied with success to demonstrate the truths of religion, while Locke includes morality along with mathematics among the a priori and certain sciences. But the history of eighteenth century controversy showed that, in spite of rationalist methods, neither morality nor religion could attain that certainty and general agreement which marked the mathematical sciences. Spinoza, applying the same method as Descartes, but with more consistency, arrived at a conception of God which most of his contemporaries regarded as "horrid atheism," and the general result of rational theology is well described by one of Kant's correspondents when he says that the more proofs of the existence of God he learnt, the more his doubts increased. In England the attempts made to found morality upon rationalist principles produced systems too barren to withstand the attack of empiricism fortified by the growing interest in history and anthropology. The Deist movement, an attempt to free religion from the incrustations of faith and deduce it from pure reason, showed that a religion founded on pure reason contained nothing worth believing. In Hume we have the final discrediting of reason in these spheres. He shows ingeniously that "the good Berkeley's" argument for the existence of God could be turned round to disprove the existence of the soul, and he concluded that religion was a sphere with which reason had no concern. In the sphere of morals the distinction between what ought to be and what is, the distinction on which rationalistic morals are based, had been discredited by a reduction of all conduct to Utilitarianism, a search for pleasure and a flight from pain mediated by sympathy. The consequences are described by Kant in his preface to the _Critique of Pure Reason_: "At present, after everything has been tried, so they say, and tried in vain, there reign in philosophy weariness and complete indifferentism, the mother of chaos and night in all sciences," though he hopefully continues, "but at the same time the source, or at least the prelude, of their near reform and of a new light, after an ill-applied study has rendered them dark, confused, and useless."

The earlier of the modern thinkers--Descartes among the rationalists, and Bacon among the empiricists--are full of hope. They have confidence in the human spirit. But increased reflection seemed only to bring distrust with it. The history of rationalism in theology showed that, in such matters, reason could prove absolutely opposing positions. Most men were ready to accept Hume's dictum that any one who follows his reason must be a fool and take refuge in an indifferentism which accepts whatever happens to be there.

The remedy for this state of affairs, Kant finds, is the critical method; for disbelief in reason is the reaction from overconfidence in it. Men had thought that reason could prove everything. Because these hopes had been frustrated, they now thought that it could prove nothing. Philosophy, he was convinced, would oscillate between overweening confidence and unwarranted distrust in itself until it had criticised human reason and discovered what it could do and what it could not. This is the task he set before himself. As the failure of eighteenth century philosophy, which had led to distrust of all philosophy, had been twofold--failure to give an intelligible explanation of the processes of scientific thought, and failure to find any standard by which to mediate between the conflicting claims of science and religion--the task of the critical philosophy is twofold. It attempts to explain and to justify the methods and assumptions of the sciences, and to find some solution of the conflict between theories of the world which seem to be based upon these methods and the assumptions and claims of morality and religion.

*CHAPTER II*

*KANT'S STATEMENT OF THE PROBLEM. SYNTHETIC
A PRIORI JUDGMENTS*

In the preface to the second edition of the _Critique of Pure Reason_ Kant finds the necessity of criticism in the contrast between certain rational sciences and metaphysics. Mathematics and physics, he observes, are obviously certain sciences. They are not empirical, they make steady progress, the results they have reached are secure and unanimously accepted, and have a certainty which no mere empirical investigation could attain. Metaphysics, on the other hand, though as ancient an inquiry, seems incapable of any settled results. Its history is a record, not of steady progress, but of bewildering marches and countermarches. The confident conclusions of one philosopher are as confidently denied by another, and the endless indecisive conflict produces in the minds of most men the conviction that in philosophy one doctrine is as good as another, and therefore none are worth very much. In the sphere where reason might be expected to be most at home, reason is impotent; yet the achievements of reason in those other spheres of the a priori sciences should preserve us from any general scepticism of the powers of reason. The task of criticism will be to examine the part played by reason in science, and to ask how far its failure in metaphysics is due to mistakes in method, and how far to the different nature of the objects of the a priori sciences and of metaphysics. Kant points out that it was some time before either mathematics or physics followed the secure path of a science. The contrast between the haphazard and empirical observations of the Babylonians or Egyptians and the science of the Greeks was due to the discovery of a new method. The discovery by Galileo and Torricelli of modern physics came about by a similar revolution in method. The _Critique_, therefore, is to be a treatise on method. It will examine the method of reason in the sciences, and ask what conclusions can be drawn as to the proper method of metaphysics.

In the _Prolegomena_, a work in which he summarises the results of the first _Critique_, Kant describes the _Critique_ as an answer to three questions: How is mathematics possible? How is pure science of nature or physics possible? and, How is metaphysics possible? Something of the nature of his answer to the third, and for him the most important, question, may be gathered from the fact that he explains that the third question should not be put in the form, How is metaphysics as a science possible? That question can only be answered by saying that it is not possible. But it is still allowable and necessary to ask, How is metaphysics possible as a natural disposition of the mind? For the main result of his inquiries into the place of reason in the sciences is to show that reason is successful in the sciences only because of the presence of certain conditions which are wanting in metaphysics. At first sight we might think it natural that the objects of metaphysics which Kant enumerates as God, Freedom, and Immortality should be understood by reason, and find it more difficult to explain how reason should apply to the world of ordinary experience. The knowledge of everyday things is thought of as empirical, a matter of observation; while we are inclined to think that, if there is rational knowledge, it is knowledge of something else, of the mere agreement or disagreement of ideas (as Hume thought), or of the essences of things, known independently and apart from perception, as Plato thought. Kant argues that the combination of a priori reasoning and empirical observation, which earlier thinkers had found so puzzling in the exact sciences, exhibits the only possible use of reason, that reason, divorced from and with no reference to the world of experience, is barren, and that consequently metaphysics, if that be taken to mean a rational knowledge of objects which are outside of our experience, does not exist. We are left with metaphysics as a natural disposition; for Kant holds that the questions which metaphysics seeks to answer arise from the nature of reason and its relation to experience, though their answer is to be sought not in knowledge but in action.

This last point must be elucidated later. In the meantime we must see how this inquiry into the nature of reason crystalises itself into a seemingly abstract and trivial question: How are synthetic a priori judgments possible? It is baffling at first to find an inquiry of the scope we have indicated suddenly take such a narrow form, but a little consideration will show the importance of the question. Knowledge may be regarded as either analysis or synthesis, as a puzzling out or unravelling of what we somehow know already, or as a putting together of what had previously been known or observed separately. The rationalist school, whom we described in the last chapter, were inclined to regard all knowledge as analytical. They thought of progress in knowledge as an advance from obscure to clear apprehension, and as a thinking out or making clear of something which had always been known somehow. Mathematics, the typical form of knowledge for the rationalists, had been thought of as the analysis of what was implied or given in the definitions. The conception of analytic a priori knowledge was thus familiar and simple. On the other hand, the empiricists had thought of knowledge as primarily synthesis--or, as they called it, association--a connecting together of ideas in their nature separate. Knowledge of a thing was thought of as the observing together of several ideas. Judgments about objects were regarded as judgments about the co-existence of separate ideas, ideas which were not thought of as being bound by any logical necessity. We do not understand why a substance with the specific gravity of gold should be yellow; we only observe the co-existence of certain qualities. The judgment, then, gold is yellow, is synthetic; it is an assertion of the co-existence of separate qualities. It is also empirical; it does not express a reasoned insight into the necessary connection of gold and yellow. It seems rather a record of observation. Synthetic knowledge, then, was thought of as in its nature empirical and a posteriori. Hume, who thought of all knowledge of the world in experience as synthetic, denied to such knowledge any necessity or certainty.

Hume, however, had noticed that the principle of causation, the judgment that every event has a cause, is both a priori and synthetic. It is not, he held, derived from experience; rather it is a principle which guides our investigation of experience. It is not got from analysis of the notion of causation, nor is it simply concerned with the agreement or disagreement of our ideas. It asserts the necessary connection of two perfectly separate existing things. Hume himself, as we saw, tried to explain away these uncomfortable facts. He was too wedded to his belief that all knowledge was derived from passively received impressions to face them rightly. Kant, coming to the problem with different prepossessions, with the belief that most knowledge was analytic, was impressed with Hume's proof that the principle of causation could not be derived from analysis. The very basis of all science of nature, then, contradicted the belief that knowledge was analytical. Kant was also, with Hume, convinced that the principle of causation was not derived from experience, for he saw that experience assumed it. At the same time, he was not prepared, like Hume, to explain it away. Further, he saw that the problem raised by the principle of causation was a wide one. For other judgments, he held, are both synthetic and a priori, among them mathematical judgments. As we shall see afterwards, Kant proved the impossibility of arriving at knowledge of God or the soul by mere analysis of concepts. The judgments of metaphysics, about God or the soul, are also synthetic. But the validity of the judgments of metaphysics is under dispute. If we examine the synthetic a priori judgments of mathematics and of science whose validity is certain, we may then discover whether such judgments in metaphysics can or can not have similar certainty. We may thus see that the problem of the possibility of synthetic a priori judgments is a restatement in logical terms of the problem of the relation between the a priori sciences and metaphysics.

Something more must be said of the importance of synthetic a priori judgments in Kant's account of knowledge. Their existence, we have seen, exposes the shortcomings of both rationalism, which allowed only for analytic a priori judgments, and empiricism, which allowed only of synthetic a posteriori judgments. Both these theories tended to regard knowledge as an analysis or description of what was present to the mind, and differed really only in their view of what was present. For, though the empiricist thought of empirical knowledge as synthesis, the synthesis was not ascribed to the mind, but to associating ideas; the mind only observed, and knowledge was merely the apprehension of objects by the senses. We see what is before our eyes, and notice the differences and similarities in what is before us. The rationalist conceived of thought as simply apprehending the nature of the real, freed from the illusions of sense perception. The mathematician has before his thought the nature of a triangle, and sees intellectually what that nature implies. We may try to mediate between the two by saying that while all knowing is observing, some is observing of objects of thought and some of objects of sense, the one being called understanding, the other perception. In most scientific judgments, however, we are not simply observing objects either of thought or of sense. Scientific judgments are more than descriptions of what is present to the mind or to the senses; they are essentially anticipations. They go beyond what is immediately given. This is shown by the fact that it is the characteristic of a scientific proposition that it can be verified. If we understand it rightly, we see that it implies that, under such-and-such conditions, such-and-such things will be experienced. Hence the importance of experiment to science. A scientific proposition is, of course, grounded on observation of perceived fact and understanding of universal connection, but it is an assertion of something beyond that.

If, then, all scientific judgments are synthetic, and if both rationalism and empiricism failed to account for the manner in which such judgments go beyond what is immediately given to the mind, ought we not to say that the real problem for Kant is to show not merely how synthetic a priori judgments are possible, but how any synthetic judgments are possible? This seems at first sight plausible, but the suggestion must be rejected; for, when Kant asks how a judgment is possible, he is not asking how we come to make it, but how we know that it is valid. Now, if we consider any empirical judgment about the facts of nature, we must recognise that Locke and Hume were right in denying certainty to such judgments. In all general statements about concrete facts we to a certain extent go beyond our evidence. Empirical scientific statements are not theoretically certain. They may, of course, be certain enough for all practical purposes. They are reasonable expectations of what will happen, but reasonable expectation is a very different thing from the certainty of mathematical insight.

Now Kant maintained that, while such empirical judgments are not certain, they all imply the certainty of a number of general principles on which they depend. These general principles are the synthetic a priori judgments with which he is especially concerned. When we apply the principles of trigonometry to an engineering problem, we know that our measurements are only approximate, and that the result also will only be approximate; but the possibility of arriving at such approximate results depends on the absolute truth of the trigonometrical principles, and on the assumption that they express not simply the agreement or disagreement of ideas, but hold of the real. When we apply the rules of arithmetic to counting objects, there may be a certain arbitrariness in deciding on our unit. There is no such arbitrariness in the rule. All scientific judgments of causation are only approximately certain, but they all imply the certainty of the principle of causation, and are based on the assumption that such a principle is of universal application. This and the other principles assumed in our empirical judgments are, then, the synthetic judgments with which Kant is concerned. Now, it is of the nature of our empirical knowledge that it is fragmentary and not uniform, that we are concerned with an indefinite number of things whose connections we do not wholly understand, and which we cannot therefore anticipate. Yet we assume that all these objects will obey the rules of arithmetic and geometry, and will all be subject in their changes to the principle of causation. On such assumptions all the sciences of applied mathematics depend. How are they justifiable? That is Kant's question.

Kant, when he considers mathematics, is concerned with the assumptions of applied mathematics, of those sciences which, though mathematical, make statements about existing objects, and in which the old distinction between understanding and perception which was based on the difference in the objects of these two faculties breaks down. The sciences which Kant is investigating imply that principles which are clearly not derived from mere observation are yet the basis on which we order and arrange what we observe. Now, if we held that the objects of mathematics were independent entities quite separate from the things we perceive, it would be impossible to explain how we might assume that the things we perceive would be subject to the rules of mathematics. If, on the other hand, we held that in mathematics we were simply concerned with the various objects of the senses, it would be impossible to explain how mathematics can have a generality and necessity which no statements can have which rest on observation of the various things we see. The existence of applied mathematics implies firstly that understanding and perception are distinct, and that neither of them can be reduced to the other, for that would mean that we should have to give up either the element of observation and experiment or the element of necessity and a priority, and secondly, that understanding and perception are combined, and must be combined for any advance in science.

Now, Kant finds his answer to the problem he has raised by concentrating his attention on the fact that, while understanding and perception are distinct, they are both present in all knowledge. His argument is that we are necessarily in a difficulty if we think of understanding and perception as having each its separate objects, and then try to explain their combination. If we begin with their combination, we may see that the reference of principles of thought to objects of sense is not an accident, but that these principles of thought or of understanding, as Kant calls them, are only concerned with objects of sense, and have no other meaning. If we object, But how can principles of thought be universal if they are concerned with the many and varying objects of sense? Kant's answer is that they are not concerned directly with these objects, but with the conditions under which these objects can be understood. They are therefore not statements about objects, but statements of the conditions of possible experience. If we find out that all perceiving and thinking imply certain conditions, then we can affirm the validity of principles based upon these conditions, so long as we do not try to apply the principles beyond our perceiving.

We may put the point in another way by asking by what right the mind can prescribe to or anticipate experience. Kant's answer is just in so far as we can determine the conditions under which alone objects can be known. If that can be done, we can say, These principles will hold of objects in so far as they are known. In the preface to the second edition of the _Critique of Pure Reason_ Kant reverts to the discoveries of Galileo and Torricelli, and points out that their success was due to their asking of nature the right question, and the right question was that which reason could understand. "When Galileo let balls of a particular weight, which he had determined himself, roll down an inclined plane, or Torricelli made the air carry a weight, which he had previously determined to be equal to that of a definite volume of water, a new light flashed on all students of nature. They comprehended that reason has insight into that only which she herself produces on her own plan, and that she must move forward with the principles of her judgments, according to fixed law, and compel nature to answer her questions, but not let herself be led by nature, as it were in leading-strings. Otherwise accidental observations, made on no previously fixed plan, will never converge towards a necessary law, which is the only thing that reason seeks or requires. Reason, holding in one hand its principles, according to which alone concordant phenomena can be admitted as laws of nature, and in the other the experiment which it has devised according to those principles, must approach nature in order to be taught by it, but not in the character of a pupil who agrees to everything the master likes, but as an appointed judge, who compels the witnesses to answer the questions which he himself proposes."

Kant, here, is concerned with reason in its application to experience, and he makes it clear that there is much in all such inquiries which cannot be anticipated a priori. "Reason must approach nature in order to be taught by it." The answer to the questions and experiments cannot be known beforehand. The empirical element in science cannot be explained away. Reason dictates not the answer but the question, and so far the form of the answer. Reason, then, it is suggested, is concerned with the principles or conditions, according to which we can understand things. It is not a method of observing or analysing objects; rather it states the methods and principles according to which objects must be observed if they are to be understood. The principles are not statements about the nature of objects, but principles of the possibility of experience. This new attitude to reason Kant describes as the Copernican change in philosophy. It constitutes Kant's idealism. Its nature and importance we must examine in the next chapter.

*CHAPTER III*

*KANT'S IDEALISM. TIME AND SPACE*

The great discovery which Kant considered he had made as to the nature of reason was that reason was not a method of observing objects as they really exist, but was concerned directly only with our ways of understanding objects. This discovery is the essence of Kant's idealism, and its main purport is expressed in the distinction Kant so often makes between things in themselves and phenomena. This distinction is used as the key to the solution of all his difficulties. But the doctrine it implies is very easy to misunderstand, partly because idealism is generally used in a very different sense from that in which Kant uses it, partly because Kant's statement of the distinction between things in themselves and phenomena depended on a view of knowledge which he was very much concerned to refute, but with which we are not now familiar. If we are to understand Kant's philosophy, we must know what he means by idealism, and wherein his idealism differs from that of his predecessors.

The word idealism is, naturally, contrasted with realism. It suggests an assertion that something is not real, but only an idea. If we know it to be combined with a distinction between things in themselves, and phenomena, or appearances, it seems to suggest that the objects of knowledge are somehow illusions, or only appearances in the mind, as contrasted with real things. Something like this had been held by Kant's predecessors. For the fundamental principle of the idealism on which most of Kant's predecessors had been agreed, and which is sometimes called Cartesian, and sometimes subjective idealism, is that the mind somehow knows itself and its own actions and states, with more directness and certainty than it knows external objects. The doctrine is commonly based upon a confused view of sense perception.

Sense perception is obviously possible only through processes in the sensory organs, and objects were thought of as producing impressions through the sensory organs in the brain, and the mind as then becoming aware of them in the brain. Hence, when Locke says that the mind only knows its own ideas, he tends to mean (though the facts are sometimes too much for him and he is nobly inconsistent) that the mind only knows objects inside the brain. The main objection to this doctrine, apart from the fact that it is based on a confusion, is that it makes it quite inexplicable how the notion of an outside world ever arises. For if we know, and must eternally know, only ideas inside our head, why should we ever imagine that there an outside world exists. Yet if nothing _outside_ us were observed--if we knew of no process which went on between outside objects and the brain, the doctrine would have no basis on which to rest. There cannot be any meaning in saying something is "only an idea," if we do not know what is real in the sense of its having an existence independent of our minds.

Locke supposed that, although we knew only ideas, we could somehow refer from our ideas to an outside world. For he thought that truth was concerned with the agreement of our ideas with reality. This form of the doctrine, the commonest, is sometimes called Representationism. For it thinks of the mind as concerned with representations, or pictures, or images which it may compare with the real objects. Its futility is obvious enough. We can only compare a picture with the thing it represents, if we can know both. If we can only know ideas, we can never know that they are only ideas, and can never compare them with anything else.

This difficulty was seen by Berkeley, the most consistent of subjective idealists, and led him to deny the existence of outside objects, and hold that existence or reality meant being perceived and nothing more. But if we take Berkeley's position, it becomes very difficult to say what we mean by judgments being true. If things only exist as we think of them, or perceive them, or rather if they are only our thinking of or perceiving them, the question of the truth or falsity of our statements about them cannot arise.

This idealism Kant is careful to refute, and he points out that there is no evidence for its fundamental proposition that we know our mind more directly than we know objects. We are only conscious of ourselves in knowing something not ourselves. We do not invent the notion of externality or outsideness in space from an experience in which it originally has no part. Externality is implied in our most simple experience. We begin with consciousness of outside things, and only become conscious of our own mental states or processes later. But it is important to observe that, the truth or falsity of subjective idealism has no bearing whatsoever on the question with which Kant was concerned. If I ask how I can lay down rules about what I have not yet experienced, I am not in the least helped by being told that I only experience what is in my mind. For the question will equally arise, How do I know what is going to be in my mind? The question idealism ordinarily discusses, as to whether the objects of our awareness are in our mind or outside, are in their nature mental and dependent on the mind or not, is entirely and absolutely irrelevant to Kant's purposes.

But it is a fact, and one that has got to be explained that in judgment we go beyond what is present to our minds, and that, in so anticipating what we shall experience, we assume that certain principles hold of all that has been or may be present. With that difficulty idealism, as ordinarily understood, has nothing to do. Representationism tried to give some account of this going beyond what is present to our minds by suggesting that truth is a reference from ideas to reality; but, as we saw, if we know only ideas, such a reference is impossible. The doctrines opposed to representationism, that only ideas exist, or that we directly know real objects, allow the existence of nothing contrasted with what we are apprehending to which a reference in judgment can be made. No one who is satisfied with any of these positions can have seen Kant's problem.

If Kant then, is not a subjective idealist what does he mean by saying, as he constantly does, that we only know phenomena, and why should that limitation of knowledge help him in any of his difficulties? He means, in the first place, that all knowledge depends upon perception. The first paragraph of the first part of the _Critique of Pure Reason_ makes that clear. "Whatever the process and the means may be by which knowledge reaches its objects, there is one that reaches them directly and forms the ultimate material of all thought, viz. perception. This is possible only when the object is given, and the object can be given only (to human beings, at least) through a certain affection of the mind."

Now, although we perceive an objective reality, sense perception obviously gives a very imperfect knowledge of objects. We see only some sides and aspects of things, and not others. What we see depends on changes in our position. Further, we know that what we see is only a small part of the nature of anything. We think of reality as an interconnected system, but we only perceive a very small part of it, and what we perceive depends upon the particular time and the particular part of space in which we live. In our experience we are never really content simply with what we perceive; we perceive much too little for that. We are always inferring from what we see to something beyond it. What is that something beyond, which, as we have seen, is implied in all judgment? We might hold that it was the things as they really are as distinguished from things as they appear, or phenomena, and that, when we turned from perception to thought, we turned from illusion to reality. Kant denied this. He held that, if you examine a scientific judgment about anything you perceive, such as that yellow thing is gold, you will find that, if you know what the judgment means, you will be able to say: Then, under such-and-such conditions--if you weigh it, for example--you will have such-and-such a perception. The appeal is not from what you perceive to what you think, but from what you perceive now to what you will perceive under such-and-such conditions. Such a reference indeed, implies thought and what is ordinarily called a concept; but our knowledge of concepts used in science always means that, if we know what is meant _e.g._ by calling anything gold, we know how it will behave under such-and-such conditions. The concept, in Kant's words, is a function of unity in our representations. The task of thought, then, is not to turn the mind away from what we perceive, but to help us to transcend some of the limitations of our perceptions, or, to speak more accurately, to set somewhat further back the limits of our perception; for thought never entirely transcends these limits. Our knowledge is always conditioned by the fact that we are finite minds living in a particular place and at a particular time; but thought can extend the range of our perception in space and in time.