Kant"s Theory of Knowledge.
by Harold Arthur Prichard.
PREFACE
This book is an attempt to think out the nature and tenability of Kant"s Transcendental Idealism, an attempt animated by the conviction that even the elucidation of Kant"s meaning, apart from any criticism, is impossible without a discussion on their own merits of the main issues which he raises.
My obligations are many and great: to Caird"s _Critical Philosophy of Kant_ and to the translations of Meiklejohn, Max Muller, and Professor Mahaffy; to Mr. J. A. Smith, Fellow of Balliol College, and to Mr. H.
W. B. Joseph, Fellow of New College, for what I have learned from them in discussion; to Mr. A. J. Jenkinson, Fellow of Brasenose College, for reading and commenting on the first half of the MS.; to Mr. H. H.
Joachim, Fellow of Merton College, for making many important suggestions, especially with regard to matters of translation; to Mr.
Joseph, for reading the whole of the proofs and for making many valuable corrections; and, above all, to my wife for constant and unfailing help throughout, and to Professor Cook Wilson, to have been whose pupil I count the greatest of philosophical good fortunes. Some years ago it was my privilege to be a member of a cla.s.s with which Professor Cook Wilson read a portion of Kant"s _Critique of Pure Reason_, and subsequently I have had the advantage of discussing with him several of the more important pa.s.sages. I am especially indebted to him in my discussion of the following topics: the distinction between the Sensibility and the Understanding (pp. 27-31, 146-9, 162-6), the term "form of perception" (pp. 37, 40, 133 fin.-135), the _Metaphysical Exposition of s.p.a.ce_ (pp. 41-8), Inner Sense (Ch. V, and pp. 138-9), the _Metaphysical Deduction of the Categories_ (pp.
149-53), Kant"s account of "the reference of representations to an object" (pp. 178-86), an implication of perspective (p. 90), the impossibility of a "theory" of knowledge (p. 245), and the points considered, pp. 200 med.-202 med., 214 med.-215 med., and 218. The views expressed in the pages referred to originated from Professor Cook Wilson, though it must not be a.s.sumed that he would accept them in the form in which they are there stated.
CHAPTER I
THE PROBLEM OF THE _CRITIQUE_
The problem of the _Critique_ may be stated in outline and approximately in Kant"s own words as follows.
Human reason is called upon to consider certain questions, which it cannot decline, as they are presented by its own nature, but which it cannot answer. These questions relate to G.o.d, freedom of the will, and immortality. And the name for the subject which has to deal with these questions is metaphysics. At one time metaphysics was regarded as the queen of all the sciences, and the importance of its aim justified the t.i.tle. At first the subject, propounding as it did a dogmatic system, exercised a despotic sway. But its subsequent failure brought it into disrepute. It has constantly been compelled to retrace its steps; there has been fundamental disagreement among philosophers, and no philosopher has successfully refuted his critics. Consequently the current att.i.tude to the subject is one of weariness and indifference.
Yet humanity cannot really be indifferent to such problems; even those who profess indifference inevitably make metaphysical a.s.sertions; and the current att.i.tude is a sign not of levity but of a refusal to put up with the illusory knowledge offered by contemporary philosophy. Now the objects of metaphysics, G.o.d, freedom, and immortality, are not objects of experience in the sense in which a tree or a stone is an object of experience. Hence our views about them cannot be due to experience; they must somehow be apprehended by pure reason, i. e. by thinking and without appeal to experience. Moreover, it is in fact by thinking that men have always tried to solve the problems concerning G.o.d, freedom, and immortality. What, then, is the cause of the unsatisfactory treatment of these problems and men"s consequent indifference? It must, in some way, lie in a failure to attain the sure scientific method, and really consists in the neglect of an inquiry which should be a preliminary to all others in metaphysics.
Men ought to have begun with a critical investigation of pure reason itself. Reason should have examined its own nature, to ascertain in general the extent to which it is capable of attaining knowledge without the aid of experience. This examination will decide whether reason is able to deal with the problems of G.o.d, freedom, and immortality at all; and without it no discussion of these problems will have a solid foundation. It is this preliminary investigation which the _Critique of Pure Reason_ proposes to undertake. Its aim is to answer the question, "How far can reason go, without the material presented and the aid furnished by experience?" and the result furnishes the solution, or at least the key to the solution, of all metaphysical problems.
Kant"s problem, then, is similar to Locke"s. Locke states[1] that his purpose is to inquire into the original, certainty, and extent of human knowledge; and he says, "If, by this inquiry into the nature of the understanding I can discover the powers thereof; how far they reach, to what things they are in any degree proportionate, and where they fail us; I suppose it may be of use to prevail with the busy mind of man, to be more cautious in meddling with things exceeding its comprehension; to stop when it is at the utmost extent of its tether; and to sit down in a quiet ignorance of those things, which, upon examination, are found to be beyond the reach of our capacities."
Thus, to use Dr. Caird"s a.n.a.logy,[2] the task which both Locke and Kant set themselves resembled that of investigating a telescope, before turning it upon the stars, to determine its competence for the work.
[1] Locke"s _Essay_, i, 1, ---- 2, 4.
[2] Caird, i, 10.
The above outline of Kant"s problem is of course only an outline. Its definite formulation is expressed in the well-known question, "How are _a priori_ synthetic judgements possible?"[3] To determine the meaning of this question it is necessary to begin with some consideration of the terms "_a priori_" and "synthetic".
[3] B. 19, M. 12.
While there is no difficulty in determining what Kant would have recognized as an _a priori_ judgement, there is difficulty in determining what he meant by calling such a judgement _a priori_. The general account is given in the first two sections of the Introduction. An _a priori_ judgement is introduced as something opposed to an _a posteriori_ judgement, or a judgement which has its source in experience. Instances of the latter would be "This body is heavy", and "This body is hot". The point of the word "experience" is that there is direct apprehension of some individual, e. g. an individual body. To say that a judgement has its source in experience is of course to imply a distinction between the judgement and experience, and the word "source" may be taken to mean that the judgement depends for its validity upon the experience of the individual thing to which the judgement relates. An _a priori_ judgement, then, as first described, is simply a judgement which is not _a posteriori_. It is independent of all experience; in other words, its validity does not depend on the experience of individual things. It might be ill.u.s.trated by the judgement that all three-sided figures must have three angles. So far, then, no positive meaning has been given to _a priori_.[4]
[4] Kant is careful to exclude from the cla.s.s of _a priori_ judgements proper what may be called relatively _a priori_ judgements, viz. judgements which, though not independent of all experience, are independent of experience of the facts to which they relate. "Thus one would say of a man who undermined the foundations of his house that he might have known _a priori_ that it would fall down, i. e. that he did not need to wait for the experience of its actual falling down. But still he could not know this wholly _a priori_, for he had first to learn through experience that bodies are heavy and consequently fall, if their supports are taken away." (B. 2, M. 2.)
Kant then proceeds, not as we should expect, to state the positive meaning of _a priori_; but to give tests for what is _a priori_. Since a test implies a distinction between itself and what is tested, it is implied that the meaning of _a priori_ is already known.[5]
[5] It may be noted that in this pa.s.sage (Introduction, ---- 1 and 2) Kant is inconsistent in his use of the term "pure".
Pure knowledge is introduced as a species of _a priori_ knowledge: "_A priori_ knowledge, if nothing empirical is mixed with it, is called pure". (B. 3, M. 2, 17.) And in accordance with this, the proposition "every change has a cause" is said to be _a priori_ but impure, because the conception of change can only be derived from experience. Yet immediately afterwards, pure, being opposed in general to empirical, can only mean _a priori_. Again, in the phrase "pure _a priori_" (B. 4 fin., M. 3 med.), the context shows that "pure" adds nothing to "_a priori_", and the proposition "every change must have a cause" is expressly given as an instance of pure _a priori_ knowledge. The inconsistency of this treatment of the causal rule is explained by the fact that in the former pa.s.sage he is thinking of the conception of change as empirical, while in the latter he is thinking of the judgement as not empirical. At bottom in this pa.s.sage "pure" simply means _a priori_.
The tests given are necessity and strict universality.[6] Since judgements which are necessary and strictly universal cannot be based on experience, their existence is said to indicate another source of knowledge. And Kant gives as ill.u.s.trations, (1) any proposition in mathematics, and (2) the proposition "Every change must have a cause".
[6] In reality, these tests come to the same thing, for necessity means the necessity of connexion between the subject and predicate of a judgement, and since empirical universality, to which strict universality is opposed, means numerical universality, as ill.u.s.trated by the proposition "All bodies are heavy", the only meaning left for strict universality is that of a universality reached not through an enumeration of instances, but through the apprehension of a necessity of connexion.
So far Kant has said nothing which determines the positive meaning of _a priori_. A clue is, however, to be found in two subsequent phrases.
He says that we may content ourselves with having established as a fact the pure use of our faculty of knowledge.[7] And he adds that not only in judgements, but even in conceptions, is an _a priori_ origin manifest.[8] The second statement seems to make the _a priori_ character of a judgement consist in its origin. As this origin cannot be experience, it must, as the first statement implies, lie in our faculty of knowledge. Kant"s point is that the existence of universal and necessary judgements shows that we must possess a faculty of knowledge capable of yielding knowledge without appeal to experience.
The term _a priori_, then, has some reference to the existence of this faculty; in other words, it gives expression to a doctrine of "innate ideas". Perhaps, however, it is hardly fair to press the phrase "_test_ of _a priori_ judgements". If so, it may be said that on the whole, by _a priori_ judgements Kant really means judgements which are universal and necessary, and that he regards them as implying a faculty which gives us knowledge without appeal to experience.
[7] B. 5, M. 4.
[8] Ibid.
We may now turn to the term "synthetic judgement". Kant distinguishes a.n.a.lytic and synthetic judgements thus. In any judgement the predicate B either belongs to the subject A, as something contained (though covertly) in the conception A, or lies completely outside the conception A, although it stands in relation to it. In the former case the judgement is called a.n.a.lytic, in the latter synthetic.[9] "All bodies are extended" is an a.n.a.lytic judgement; "All bodies are heavy"
is synthetic. It immediately follows that only synthetic judgements extend our knowledge; for in making an a.n.a.lytic judgement we are only clearing up our conception of the subject. This process yields no new knowledge, for it only gives us a clearer view of what we know already. Further, all judgements based on experience are synthetic, for it would be absurd to base an a.n.a.lytical judgement on experience, when to make the judgement we need not go beyond our own conceptions.
On the other hand, _a priori_ judgements are sometimes a.n.a.lytic and sometimes synthetic. For, besides a.n.a.lytical judgements, all judgements in mathematics and certain judgements which underlie physics are a.s.serted independently of experience, and they are synthetic.
[9] B. 10, M. 7.
Here Kant is obviously right in vindicating the synthetic character of mathematical judgements. In the arithmetical judgement 7 + 5 = 12, the thought of certain units as a group of twelve is no mere repet.i.tion of the thought of them as a group of five added to a group of seven.
Though the same units are referred to, they are regarded differently.
Thus the thought of them as twelve means either that we think of them as formed by adding one unit to a group of eleven, or that we think of them as formed by adding two units to a group of ten, and so on. And the a.s.sertion is that the same units, which can be grouped in one way, can also be grouped in another. Similarly, Kant is right in pointing out that the geometrical judgement, "A straight line between two points is the shortest," is synthetic, on the ground that the conception of straightness is purely qualitative,[10] while the conception of shortest distance implies the thought of quant.i.ty.
[10] Straightness means ident.i.ty of direction.
It should now be an easy matter to understand the problem expressed by the question, "How are _a priori_ synthetic judgements possible?"
Its substance may be stated thus. The existence of _a posteriori_ synthetic judgements presents no difficulty. For experience is equivalent to perception, and, as we suppose, in perception we are confronted with reality, and apprehend it as it is. If I am asked, "How do I know that my pen is black or my chair hard?" I answer that it is because I see or feel it to be so. In such cases, then, when my a.s.sertion is challenged, I appeal to my experience or perception of the reality to which the a.s.sertion relates. My appeal raises no difficulty because it conforms to the universal belief that if judgements are to rank as knowledge, they must be made to conform to the nature of things, and that the conformity is established by appeal to actual experience of the things. But do _a priori_ synthetic judgements satisfy this condition? Apparently not. For when I a.s.sert that every straight line is the shortest way between its extremities, I have not had, and never can have, experience of all possible straight lines. How then can I be sure that all cases will conform to my judgement? In fact, how can I antic.i.p.ate my experience at all? How can I make an a.s.sertion about any individual until I have had actual experience of it? In an _a priori_ synthetic judgement the mind in some way, in virtue of its own powers and independently of experience, makes an a.s.sertion to which it claims that reality must conform. Yet why should reality conform? _A priori_ judgements of the other kind, viz. a.n.a.lytic judgements, offer no difficulty, since they are at bottom tautologies, and consequently denial of them is self-contradictory and meaningless. But there is difficulty where a judgement a.s.serts that a term B is connected with another term A, B being neither identical with nor a part of A. In this case there is no contradiction in a.s.serting that A is not B, and it would seem that only experience can determine whether all A is or is not B. Otherwise we are presupposing that things must conform to our ideas about them.
Now metaphysics claims to make _a priori_ synthetic judgements, for it does not base its results on any appeal to experience. Hence, before we enter upon metaphysics, we really ought to investigate our right to make _a priori_ synthetic judgements at all. Therein, in fact, lies the importance to metaphysics of the existence of such judgements in mathematics and physics. For it shows that the difficulty is not peculiar to metaphysics, but is a general one shared by other subjects; and the existence of such judgements in mathematics is specially important because there their validity or certainty has never been questioned.[11] The success of mathematics shows that at any rate under certain conditions _a priori_ synthetic judgements are valid, and if we can determine these conditions, we shall be able to decide whether such judgements are possible in metaphysics. In this way we shall be able to settle a disputed case of their validity by examination of an undisputed case. The general problem, however, is simply to show what it is which makes _a priori_ synthetic judgements as such possible; and there will be three cases, those of mathematics, of physics, and of metaphysics.
[11] Kant points out that this certainty has usually been attributed to the a.n.a.lytic character of mathematical judgements, and it is of course vital to his argument that he should be successful in showing that they are really synthetic.
The outline of the solution of this problem is contained in the Preface to the Second Edition. There Kant urges that the key is to be found by consideration of mathematics and physics. If the question be raised as to what it is that has enabled these subjects to advance, in both cases the answer will be found to lie in a change of method.
"Since the earliest times to which the history of human reason reaches, mathematics has, among that wonderful nation the Greeks, followed the safe road of a science. Still it is not to be supposed that it was as easy for this science to strike into, or rather to construct for itself, that royal road, as it was for logic, in which reason has only to do with itself. On the contrary, I believe that it must have remained long in the stage of groping (chiefly among the Egyptians), and that this change is to be ascribed to a _revolution_, due to the happy thought of one man, through whose experiment the path to be followed was rendered unmistakable for future generations, and the certain way of a science was entered upon and sketched out once for all.... A new light shone upon the first man (Thales, or whatever may have been his name) who demonstrated the properties of the isosceles triangle; for he found that he ought not to investigate that which he saw in the figure or even the mere conception of the same, and learn its properties from this, but that he ought to produce the figure by virtue of that which he himself had thought into it _a priori_ in accordance with conceptions and had represented (by means of a construction), and that in order to know something with certainty _a priori_ he must not attribute to the figure any property other than that which necessarily follows from that which he has himself introduced into the figure, in accordance with his conception."[12]
[12] B. x-xii, M. xxvi.
Here Kant"s point is as follows. Geometry remained barren so long as men confined themselves either to the empirical study of individual figures, of which the properties were to be discovered by observation, or to the consideration of the mere conception of various kinds of figure, e. g. of an isosceles triangle. In order to advance, men had in some sense to produce the figure through their own activity, and in the act of constructing it to recognize that certain features were necessitated by those features which they had given to the figure in constructing it. Thus men had to make a triangle by drawing three straight lines so as to enclose a s.p.a.ce, and then to recognize that three angles must have been made by the same process. In this way the mind discovered a general rule, which must apply to all cases, because the mind itself had determined the nature of the cases. A property B follows from a nature A; all instances of A must possess the property B, because they have solely that nature A which the mind has given them and whatever is involved in A. The mind"s own rule holds good in all cases, because the mind has itself determined the nature of the cases.
Kant"s statements about physics, though not the same, are a.n.a.logous.
Experiment, he holds, is only fruitful when reason does not follow nature in a pa.s.sive spirit, but compels nature to answer its own questions. Thus, when Torricelli made an experiment to ascertain whether a certain column of air would sustain a given weight, he had previously calculated that the quant.i.ty of air was just sufficient to balance the weight, and the significance of the experiment lay in his expectation that nature would conform to his calculations and in the vindication of this expectation. Reason, Kant says, must approach nature not as a pupil but as a judge, and this att.i.tude forms the condition of progress in physics.
The examples of mathematics and physics suggest, according to Kant, that metaphysics may require a similar revolution of standpoint, the lack of which will account for its past failure. An attempt should therefore be made to introduce such a change into metaphysics. The change is this. Hitherto it has been a.s.sumed that our knowledge must conform to objects. This a.s.sumption is the real cause of the failure to extend our knowledge _a priori_, for it limits thought to the a.n.a.lysis of conceptions, which can only yield tautological judgements.
Let us therefore try the effect of a.s.suming that objects must conform to our knowledge. Herein lies the Copernican revolution. We find that this reversal of the ordinary view of the relation of objects to the mind enables us for the first time to understand the possibility of _a priori_ synthetic judgements, and even to demonstrate certain laws which lie at the basis of nature, e. g. the law of causality. It is true that the reversal also involves the surprising consequence that our faculty of knowledge is incapable of dealing with the objects of metaphysics proper, viz. G.o.d, freedom, and immortality, for the a.s.sumption limits our knowledge to objects of possible experience. But this very consequence, viz. the impossibility of metaphysics, serves to test and vindicate the a.s.sumption. For the view that our knowledge conforms to objects as things in themselves leads us into an insoluble contradiction when we go on, as we must, to seek for the unconditioned; while the a.s.sumption that objects must, as phenomena, conform to our way of representing them, removes the contradiction[13].
Further, though the a.s.sumption leads to the denial of speculative knowledge in the sphere of metaphysics, it is still possible that reason in its practical aspect may step in to fill the gap. And the negative result of the a.s.sumption may even have a positive value. For if, as is the case, the moral reason, or reason in its practical aspect, involves certain postulates concerning G.o.d, freedom, and immortality, which are rejected by the speculative reason, it is important to be able to show that these objects fall beyond the scope of the speculative reason. And if we call reliance on these postulates, as being presuppositions of morality, faith, we may say that knowledge must be abolished to make room for faith.
[13] Cf. pp. 101-2.
This answer to the main problem, given in outline in the Preface, is undeniably plausible. Yet examination of it suggests two criticisms which affect Kant"s general position.
In the first place, the parallel of mathematics which suggests the "Copernican" revolution does not really lead to the results which Kant supposes. Advance in mathematics is due to the adoption not of any conscious a.s.sumption but of a certain procedure, viz. that by which we draw a figure and thereby see the necessity of certain relations within it. To preserve the parallel, the revolution in metaphysics should have consisted in the adoption of a similar procedure, and advance should have been made dependent on the application of an at least quasi-mathematical method to the objects of metaphysics.
Moreover, since these objects are G.o.d, freedom, and immortality, the conclusion should have been that we ought to study G.o.d, freedom, and immortality by somehow constructing them in perception and thereby gaining insight into the necessity of certain relations. Success or failure in metaphysics would therefore consist simply in success or failure to see the necessity of the relations involved. Kant, however, makes the condition of advance in metaphysics consist in the adoption not of a method of procedure but of an a.s.sumption, viz. that objects conform to the mind. And it is impossible to see how this a.s.sumption can a.s.sist what, on Kant"s theory, it ought to have a.s.sisted, viz. the study of G.o.d, freedom, and immortality, or indeed the study of anything. In geometry we presuppose that individual objects conform to the universal rules of relation which we discover. Now suppose we describe a geometrical judgement, e. g. that two straight lines cannot enclose a s.p.a.ce, as a mental law, because we are bound to think it true. Then we may state the presupposition by saying that objects, e. g. individual pairs of straight lines, must conform to such a mental law. But the explicit recognition of this presupposition and the conscious a.s.sertion of it in no way a.s.sist the solution of particular geometrical problems. The presupposition is really a condition of geometrical thinking at all. Without it there is no geometrical thinking, and the recognition of it places us in no better position for the study of geometrical problems. Similarly, if we wish to think out the nature of G.o.d, freedom, and immortality, we are not a.s.sisted by a.s.suming that these objects must conform to the laws of our thinking. We must presuppose this conformity if we are to think at all, and consciousness of the presupposition puts us in no better position. What is needed is an insight similar to that which we have in geometry, i. e. an insight into the necessity of the relations under consideration such as would enable us to see, for example, that being a man, as such, involves living for ever.