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Royal Institute of Philosophy

Kant and Natural ScienceAuthor(s): B. M. LaingReviewed work(s):Source: Philosophy, Vol. 19, No. 74 (Nov., 1944), pp. 216-232Published by: Cambridge University Press on behalf of Royal Institute of PhilosophyStable URL: http://www.jstor.org/stable/3748175 .Accessed: 03/02/2012 18:17

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KANT AND NATURAL SCIENCEB. M. LAING, M.C., M.A., D.LIrr.

THE itle of this article might quite well be given the more hackneyedform, Has Kant answered Hume? Much of the discussion pertainsto this latter question, but as the aim is also to emphasize somepoints concerned with Kant himself a deviation in title may bepermissible.

From among the different types of proposition which Kant recog-nizes he selects the synthetic a priori type as his main subject ofinvestigation. This type raises the twofold query--what are themeanings of the words a priori and synthetic There are obscuritiesin Kant's doctrine, and it may even be said that his own examplesof a priori and of synthetic propositions are not very fortunate,though of course this fact does not of itself invalidate the theory hewishes to

expound:better

examples mightbe

forthcoming.Other

requirements, however, must be fulfilled, and they will be noted indue course. One consequence of the obscurity appears in an inter-pretation and criticism which have sometimes been made even bydistinguished Kantian commentators.' It has been said that thedistinction between analytic and synthetic judgments, as exemplifiedin body is extended and body has weight, is not absolute sincethe former, as Kant himself says,2 was originally derived from

experience and is therefore synthetic, while on the other hand the

latter judgment must be regarded as an analytical one when onceit has become a part of the mind's mental furniture, since the con-

ception body then includes the conception weight as a logicalpart of itself. This reading would make the distinction vanish in a

peculiarity of psychology. It is possible that Kant's examples oughtto be considered both in relation to the historical controversy aboutthe fundamental properties of matter and to the rationalist view,expressed in Cartesianism, hat the essence or fundamental propertyof matter is extension. If this is so and if the above interpretationof Kant's distinction is correct, doubt must be felt whether Kantheld that the predicate extended which is asserted of body isderived from experience, or if he did, whether he is quite in accordwith Cartesianism for Descartes probably did not maintain that itwas. Apart from this, however, the proposition body is extended

requires on Kant's theory to be regarded as asserting a predicateI E.g. Watson: Philosophy of Kant Explained, pp. 58-59. See also T. H.

Green: Works, II, p. 6i. 2 Watson is being quoted.

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which is contained already in the subject-notion, namely body. Apoint which Kant may have in view and which is very important

if his doctrine is not to dissolve into psychologism must not beoverlooked. On the interpretation given above the necessity whichcharacterizes some propositions is reduced to a psychological com-pulsion to express what is one's notion of a body: there is noguarantee that this notion is correct, and hence the necessity orcompulsion s relative.

Now what Kant assumed was that the proposition body isextended is true, that the predicate expresses the essence of bodyin a logical sense, and that the necessity of the proposition, conse-

quently of all a priori propositions, is a logical necessity which isprior to and conditions the psychological compulsion. One may bepermitted to question whether this doctrine of essence and logicalnecessity need be assumed, for the necessity which is apprehendedand about which the dispute rages may be merely the necessity ofhaving a minimal property if we are to talk about, or claim toapprehend, body at all. The relevant point about the proposition

body is heavy or body has weight, said to be synthetic, is thatthe property of weight cannot be logically deduced from, or is notlogically implied in, the property of extension. This being so, Kanthas to regard it as in a logical sense an addition to the propertyof extension, and hence arises his problem as to how the additioncan be related to the extension, that is a problem of synthesis.IThe latter term for Kant signifies unity, and his problem becomesone of conceiving how a body is or can be a unity seeing that it hasa number of logically unconnected properties. What underlies Kant'sargument is the assumption that since the oneness of an object

cannot be conceived, in view of its logically disconnected properties,as a logical unity of properties implied in or deducible from anessence or fundamental property, that oneness must be sought inthe general conception of body itself, even though in so doing hemay be open to the criticism that all his subsequent argumentamounts to little more than a repeated re-assertion of the point thata body is a unity of various properties. This logical interpretationof Kant's meaning when he uses such phrases as being containedin the subject-notion or being additional to what is so contained

is in conformity with the rationalist tradition in which he wastrained, removes the psychologism and relativity which otherwisewould affect his distinction, and throws light upon his admission

It might be noted in passing that Descartes has the very same problem;it appears in connection with sense-experience and its status as knowledge.He has to make use of the Deity to justify the synthesis of sense-qualitieswith extension or else sense-experience never is knowledge at all. Whichalternative is the view of Descartes is not very clear. Kant's variation onDescartes' theme is interesting.

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that the issue does not depend upon the presence or absence ofempirical elements in the proposition.

But the propositions with which Kant is concerned are not merelysynthetic ones: they are also a priori. Unfortunately the worda priori has come to be used in many diverse senses, and it is to befeared it is so used by Kant himself. There is one clear and precisemeaning which he attaches to it, namely necessity and universality;but it also, in virtue of his views about necessity and universality,comes to mean what is independent of experience and even as whatis contributed by the mind. The problem of the synthetic a prioriproposition, now considered with reference to this a priori character,accordingly becomes one as to how a predicate or a property thatis not contained in the subject-notion can be asserted of, orcan be known to be related to, the subject-notion in a manner thatis necessary and universal. An interpretation nvolving psychologismdoes not permit of any ground for the defence of this universalityand necessity in the sense in which Kant obviously wishes to main-tain it. His point, whether he always expresses himself consistentlyor not on this matter, is that universality and necessity characterizethe proposition and they do so because and in so far as they arefeatures of a relation between the subject and predicate of theproposition and not because they are features of a relation betweenthe knower and the subject of the proposition. The significance ofthe a priori for Kant is, not so much, if at all, that the subject ofthe predicate or both cannot be derived from experience, but thatthe relation between subject and predicate where that relation ismarked by necessity and universality cannot be derived fromexperience. Kant's own examples, as well as his form of statement,

are unfortunate because they suggest that the distinction betweenanalytic and synthetic propositions and consequently, since theformer is always a priori, the distinction likewise between a prioriand a posteriori, depend on whether the predicate (and even thesubjects) of propositions are or are not derived from experience,this in turn presupposing that there are propositions whose subjectsor predicates or both are not derived from experience. There ishere a source of obscurity which pervades Kant's whole expositionand which would render absurd any pure a priori knowledge r prin-ciples having the status of knowledge, or knowledge requires botha priori and sensuous factors, the former without the latter being

empty. The obscurity can be avoided, although no claim can bemade that difficulties can be removed, by recognizing that thematter of the proposition is not being brought under discussion atall but that it is the form, the relational factor, that is in question.What is therefore at issue is not whether the matter-subject andpredicate-of the proposition is derived from or is dependent on2I8

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experience but whether the relation, and especially certain propertiesof the relation, between subject and predicate are derived from and

are dependent on experience. Thus Kant might quite consistentlyadmit that in the proposition body is extended, though it isanalytic, the predicate extended was originally derived fromexperience; it could be so derived and yet be apprehended as

contained in the notion of body; but this is not the case withsynthetic or even with synthetic a priori propositions. What Kantwas anxious to illustrate by his examples was what he intended tomean by the a priori and what he conceived to be the problemconnected with synthetic a priori propositions. In this attempt to

interpret Kant's meaning only elucidation is being aimed at; anda caution must be entered against assuming that any concession isbeing made in favour of Kant that subject and predicate are notrelevant to our knowledge of the relational factor and that thenature of subject and predicate has no important bearing upon thecharacter of the relation between them.

It is always possible to raise the question whether there are anysynthetic a priori propositions. This question has been much debated,and both affirmative and

negativeanswers have been

given.There

is no intention to debate this issue at present. What, however, maybe discussed is a confusion in Kant's own exposition about thismatter, a confusion which it may be provisionally suggested hasbeen responsible for much of that indecisive debate. Kant declaresthat there are such synthetic a priori propositions; they are foundin mathematics and in natural science. Mathematical judgments,he says, are always synthetical, and proper mathematical proposi-tions are always judgments a priori and not empirical. The science

of natural philosophy or physics contains in itself judgments a priorias principles. Hence Kant gives an alternative formulation to hisproblem: how is pure mathematical science possible, and how ispure natural science possible ? These questions, since synthetic a prioripropositions are declared already to exist, refer to the conditionswhich are presupposed in the making of such propositions andwhich are discoverable by analysis. Having formulated his problemin the form of these questions Kant goes on to consider metaphysicsand whether it is or is not possible as a science. One result of histheory is that metaphysics as a science is not possible, and at thesame time it seeks to explain why it is not possible. In the presentdiscussion which now reaches the main topic the possibility ofmathematics or the synthetic a priori character of mathematicalpropositions s left aside and attention is concentrated on the secondquestion-the possibility of physical science.

Kant's theory has generally been accepted as a refutation ofempiricism, especially of Hume. He finds fault with Hume for not

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conceiving his problem universally. Hume, he says, stopped shortat the synthetical proposition of the connection of an effect with its

cause and hence all that we term metaphysical science is a meredelusion. I He seems to think that a denial of the a priori characterof the principle of causation carries with it also a denial of thesynthetic a priori character of mathematics, for he goes on to declarethat Hume would not have been led to such a result if he had viewedthe problem universally, for he would then have seen that accordingto his argument there could not likewise be any pure mathematicalscience. To this criticism an answer may be given in passing. First,Hume's view of mathematics is not quite so easily disposed of as

Kant seems to suppose, even though it may have defects, for thoughhe questioned the precision and accuracy of geometry he maintainedthat algebra and arithmetic were perfectly exact and certain.2Critics are apt to overlook the fact that Hume sought to draw adistinction between mathematical knowledge and physical know-ledge in order to emphasize the very special problem which heconceived to be involved in the latter. Second, the view that meta-physics is a delusion, for which Kant condemns Hume's theory,finds confirmation in Kant's own doctrine regarding the impossi-bility of metaphysics as a science; hence one is tempted to drawthe conclusion that, since the same consequence follows both onthe rejection and the acceptance of the synthetic a priori characterof the causal principle, this synthetic a priori character has norelevance to the possibility of metaphysics nor has the conceivingof the problem of a priori synthesis in a universal form any suchrelevance.

Kant's charge against Hume that he failed to conceive the pro-

blem universally must not be allowed to pass without attentionbeing drawn to what Kant is assuming. Why should Kant declarethat because Hume did not view the issue universally he did notsee that his rejection of the synthetic a priori character of the causalprinciple committed him to the rejection of synthetic a priori pro-positions in other spheres, for example in mathematics, and Kantsuggests at first in metaphysics? Is there any justification for thisdeclaration which is to the effect that not merely did Hume not seewhat was involved but that whether he was aware of it or not he

was logically committed to a universal denial of synthetic a prioripropositions n virtue of his denial of the synthetic a priori characterof the causal principle? It is certainly difficult to find any justifi-cation for this contention. It would be sound if it were true that allscientific propositions are a priori or else none are. But this cannotbe admitted, and it is doubtful whether any contemporary neo-

Critique of Pure Reason: Introd. VI.2Treatise of Human Nature, Bk. I, Part III, Sect. i.

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Kantians have sought to maintain any such assertion. It would besound if it were true that all scientific propositions, whatever be

the science, are and must be a priori (as well as synthetic), thattheir a priori character is in all cases traceable to one commonsource, and that to impugn this character in one case is to impugnit in all cases. Something like this set of propositions seems to bepresent to, and to influence, Kant's mind: he is quite definite aboutthe first, the second expresses what he attempts to expound and isof course a mere matter of theory the effectiveness of which is con-ditioned by the truth of the first proposition, the third is in no wayconvincing.

To appreciate certain features of Kant's doctrine and especiallyhis view of the synthetic a priori character of propositions of phy-sical science it is worth while, indeed essential, to clarify for purposesof contrast Hume's problem as stated by himself. Hume's problemhad two stages. First, what is called knowledge (that is physicalknowledge) is made up of propositions concerning matters of fact,propositions such as bread will always nourish, water will suffo-cate, and all those propositions which make up the laws of nature,all

being propositionswhich

thoughbased on

presentand

pastexperience yet assert something that goes beyond present and pastexperience. Second, the question arises as to the basis on which weform such propositions; it is a subject worthy of curiosity toinquire what is the nature of that evidence which assures us of anyreal existence and matter of fact beyond the present testimonyof our senses or the records of our memory. ' Hume proceeds toexamine the causal principle because it is generally accepted as thebasis on which propositions concerning matters of fact are formu-

lated; and his examination must always be considered in referenceto this issue. The kind of propositions in which Hume is interestedmust not be allowed to drop out of sight; his concentration on thecausal principle is subsidiary to his interest in factual propositions.

This somewhat summary statement of Hume's problem is all thatis necessary for the present purpose. Kant in dealing with physicalscience does not confine himself to the causal principle, but thelatter is one of the principles and undoubtedly for Kant a veryimportant one. Now at the present day it would be rash to laydown any rigid line of distinction between laws that belong to thebody of a science and laws that do not. It is, however, possible toassert that the principle of causation is not in the ordinary sensea scientific proposition, certainly not in the sense in which the GasLaws or the Law of Gravitation are scientific laws. Kant seems to

Enquiry, Sect. iv, Part i. cf. Treatise, |Bk. I, Part III, Sect. ii and iii,which is not in the formulation of the problem fundamentally different fromthe Enquiry.

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recognize this for he goes on to talk about a pure physics (sometimesthe term general physics appears), possibly on the analogy of, and

possibly misled by the idea of, a pure mathematics. Pure mathe-matics is what is commonly understood as mathematical science;pure physics according to Kant consists of certain propositionswhich are commonly treated at the commencement of proper(empirical) physical science, I and he is at pains to assert specificallythat there is such a pure physics. Obviously there is not a puremathematics standing in the same relation to mathematics (theword proper would have to be added to secure correspondence withKant's distinction within physics) as pure physics, in the senseconceived by Kant, stands to physics proper. (There is the modemdistinction between pure and applied mathematics, but this doesnot appear relevant to Kant's distinction within physics.) If theanalogy is accepted and stressed, then pure mathematics ought tobe a matter of the axioms, definitions, and postulates solely-whichis not the case. An examination of these axioms, etc., is really anepistemological or philosophical problem, even though it may becarried out by philosophically-minded mathematicians. But Kant'sown

example (5+ 7=

12)to illustrate the nature of

synthetica priori propositions in mathematics shows that Kant did not con-ceive pure mathematics in that way.

The whole of Kant's discussion shows that it has nothing to dowith physics in any generally accepted sense. At most there is thisto be said in justification of Kant, namely that in his own timephysics was usually spoken of as natural philosophy which onaccount of purely historical incidents included a good deal of dis-cussion of propositions supposed to be valid of physical nature and

which because of this was a mixture of philosophy and physics toan extent which would be probably now rejected. Physics does nottreat of, or try to establish, synthetical principles of the under-standing, what Kant calls axioms of Intuition, anticipationsof perception, analogies of experience, postulates of empiricalthought. If this were so, Kant would have to be regarded as aphysicist, a pure physicist, and his theory would be a physical one.In case this may seem to be pressing Kant too hard, it must beremembered that the principle of causation is included in purephysics and is discussed by him as one of the principles of theunderstanding, and that thus the distinction between his task andthat of pure physics vanishes. In case also there may be consideredhere only a minor and insignificant matter of nomenclature it isnecessary to point out provisionally-what will be in the sequeldeveloped more fully-that this distinction between pure physicsand physics proper or empirical sidetracks Hume's problem and

Critique of Pure Reason: Introd. VI n.

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acceptance of such a synthetic and a priori character is challenged?To-day it is not merely the case that doubt is entertained concerning

such a character but it is even the case that some of the propositions,if not all, are considered false and untenable. The principle ofcausation itself is under suspicion and is in some quarters rejected.It may be that Kant in some places writes as if he believed thathe is not merely accepting such propositions but that he is showingthem to be universal and necessary and by doing so proving themto be true. Which of the things he is doing, accepting as indubitablefact or proving such propositions and their a priori character, s whatremains obscure. Nevertheless it requires to be stressed that if thesepropositions of pure physics-and it is with these that Kant is con-cerned-are not true or even are not free of doubt, his whole theorydissolves into an attempt to prove what is not the case and cannotbe the case. Attention may be drawn in this connection to the factthat recently some philosophers, probably being anxious to makeout a case for Kant, have exerted themselves in arguing that thereare synthetic a priori propositions. The unsatisfactory nature ofsuch arguments lies in the samples of propositions produced, for

theyare of minor

significance usuallyso far as scientific doctrine

is concerned, do not contribute much to the support of Kant, anddo not, as they seem sometimes intended to do, serve to convictHume who would, and probably did, accept some of them. The mostthat could be said of Kant's synthetic a priori principles of purephysics is that they are relative to an epoch, that particularly ofKant himself or of the seventeenth and eighteenth and possibly ofthe nineteenth centuries. But this admission deprives them of thatnecessity and universality which Kant wants to assign to them, and

would tend to confirm Hume even if (as his critics generally asserthe did) le denied causation.This limitation to Kant's claims can be seen if one of the prin-

ciples he cites is examined, just for purposes of illustration, namely,that action and reaction must be always equal. It is to be presumedthat Kant had in mind one of Newton's laws of motion-onlyNewton added and opposite. Now the justification of these lawsof motion has always been a matter of difficulty and of considerablecontroversy. It is not at all, however, a clear proposition.I In fact,its interpretation depends upon the results of investigations in whatKant has called physics proper and upon the laws formulated there,and this is a point which has an important bearing upon the secondissue to be raised presently, namely, the relation of these synthetica priori principles of pure physics (Kant's terminology) to the pro-positions of physics proper. In regard to the proposition itself thereis the question as to how equality and oppositeness are decided

Broad: Scientific Thought, pp. 171 f.

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and it is not permissible to assume that it is a matter of the linejoining the two bodies. The law makes use of the two ideas of force

and direction; and the composition of forces and of motions is notmerely an arithmetical addition or subtraction. The conception offorce which is implicated raises, from the modern point of view,questions about the necessity of the conception or about its tena-bility; and if its retention is advocated then a further question hasto be raised about the kind of forces, whether Newtonian or non-Newtonian. The recent introduction of the notion of a field offorce complicates the interpretation of the law or proposition.Hence Professor Broad can write that' there is a field of force, to

which every particle is subjected when referred to the axes inquestion; but it cannot be said that the force on one particle isbalanced by an equal and opposite force on another particle. Somenon-Newtonian forces, then, it would seem, do not obey the thirdlaw . . . it is only for Newtonian forces that the third law holdsuniversally. This conclusion could, however, in theory be avoidedby the introduction of hypothetical concealed masses; so that thenon-Newtonian forces on observable masses might be regarded, asthe third law

requires,as one side of stresses between these observ-

able masses and the hypothetical concealed ones. Thus all the lawsof motion can be formally preserved relative to any frame of refer-ence, provided it is assumed that new frames imply new forces, andprovided that we are allowed to assume such concealed masses aswe need. It does not matter whether Professor Broad is right orwrong; what is relevant is that the proposition which Kant acceptsas synthetic a priori and which is accepted by him presumably astrue s one that is extremely complicated, is one that requires careful

examination and interpretation before it is possible to decide whatits nature is or what it is asserting and in what respect and withwhat qualifications it is true. It seems reasonable to insist that,before a proposition is accepted as true and as universal and neces-sary, there should be a clear understanding of what the propositionis maintaining. It seems also reasonable to point out that Kantshould have carried out a critical analysis of his synthetic a prioripropositions, and that the task of a pure physics, such as he con-ceives it, would be just to carry out such a criticism and examina-

tion. In such a case pure physics would be coincident with what isnow called a philosophy of science.

The second question to be raised is this: supposing that there aresynthetic a priori propositions constituting what Kant calls a purephysics, what bearing have they upon what Kant calls physicsproper? This is an issue which Kantian commentators pass oververy light-heartedly. Yet it is the crucial point of Kant's answer

I Scientific Thought, p. 176.

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to empiricism and to Hume in particular; and a failure to showthat the synthetic a priori propositions of pure physics guarantee

the necessity and universality of the propositions of physics properis a failure to answer Hume and renders the whole of Kant's effortotiose. Kant's task was not, as is so often mistakenly supposed,accomplished when he showed, or is supposed to have shown, thatthe causal principle is synthetic a priori; his own reaction to Humewas that the latter's view of causality undermined the possibilityof knowledge; he himself must not be allowed to get away with theclaim that by establishing the a priori character of the principle ofcausation he has automatically and without the need of any more

argument established the a priori character of empirical science,of the empirical propositions with which Hume was concerned.Kant's commentators have tended to overlook the significance ofKant's distinction between pure physics and physics proper and itsrelevance to the kind of knowledge which Hume and Kant respec-tively have in mind.

Attention has already been drawn, and is drawn again, to the factthat it is not enough, as some philosophers are doing at present, toseek to show that there are synthetic a priori propositions. A pro-position to the effect that every patch of colour has shape wouldhave been admitted by Hume as universal and necessary. Whena globe of white marble, he says,' is presented, we receive onlythe impression of a white colour disposed in a certain form, nor arewe able to separate and distinguish the colour from the form ....A person who desires us to consider the figure of a globe of whitemarble without thinking on its colour, desires an impossibility.Propositions of this kind have simply no relevance to Hume's

problem of causation and to his solution of it. What is required isan argument to show that the propositions which make up physicsas a science, that is, what Kant calls physics proper, are synthetica priori. The controversy raised by Hume was primarily about suchpropositions and only secondarily about the synthetic a prioricharacter of the law of causation. What Kant had to show was notmerely that the propositions of pure physics were universal andnecessary (that is, a priori) but that they stood in such a relationto the propositions of physics proper as to guarantee the univer-

sality and necessity of the latter. If the propositions of physicalscience (physics proper) are not shown to be synthetic a priori-withemphasis on the a priori or universality and necessity-the discus-sion about the a priori character of the causal principle ceases tohave importance so far as scientific propositions are concerned. Itwill not do therefore to argue that examples of synthetic a priori

Treatise, Bk. I, Part I, Sect. vii. But the point is fundamental to hisview of space.

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propositions exist and can be found; it is necessary to show thatthere exist synthetic a priori propositions of such a kind as are

relevant, directly or indirectly, to physics proper being a science.Unless this contention is accepted there is no point in Kant's remarkconcerning Hume that his theory of causation made all scienceimpossible. -It appears therefore that Kant is somewhat confusedabout the problem which Hume raised and about what he himselfis doing about it. If there is anything of importance in the taskwhich he undertakes it is that there are at least some propositionsthe nature of which is synthetic, universal, and necessary, if there isto be a science of physics. These propositions are either part of thebody of physical science itself, in so far as it is usually labelled anexperimental and empirical science, or else they are such as toguarantee the universality and necessity of the propositions of sucha science. If the latter requirement s not fulfilled, or cannot be so,physical science remains a body of probable propositions as it wouldbe if Hume's position were such as his critics contend it is and asit is according to the candid admission of many scientists to-day.

With this clarification of the issue it is now possible to proceedto a consideration of Kant's view. If he is not clear about the issue,it cannot be expected that he can be clear in dealing with it. Theobscurity comes in partly through his distinction between purephysics and physics proper, and partly through an attempt to viewthe problem of physical knowledge as exactly parallel with theproblem of mathematical knowledge in spite of that distinction.Consequently there are two alternatives about which a student ofKant feels hesitation: either he accepts the universality and neces-sity of the propositions of physics proper, and hence considers that

he has to show how they can be, or come to be, universal and neces-sary, or else he seeks to prove their universality and necessity byshowing how they are derived from or dependent on the a prioriprinciples of the understanding. Attention may once more bedrawn to the fact that what are in question are the propositionsof physics proper. In regard to mathematical propositions he holdsthat they are synthetic a priori because based directly upon thea priori form of space.' The difficulty is that physical propositionscannot be treated analogously to mathematical ones, partly becauseof the distinction between pure physics and physics proper to whichthere is no corresponding distinction in mathematics, and partlybecause of the unsatisfactory term based upon, for mathematicalpropositions are rather to be regarded as being concerned with theanalysis of the a priori form of space and as expressing the resultsof this analysis in a way in which the propositions of physics proper(whatever be the case with the propositions of pure physics) are not

x Critique of Pure Reason: Analytic of Principles, Ch. II, Sect. iii.

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obtained by an analysis of the categories or a priori principles ofthe understanding. The phrase based upon may possibly be used

in the case of the latter, although a doubt may be expressed whetherit conveys satisfactorily what Kant would like to assert. What hedoes, however, expressly and elaborately seek to argue is that thesynthetic a priori propositions of pure physics follow from thea priori categories of the understanding. What he has and ought toshow is that the categories of the understanding by way of theuniversal and necessary propositions of pure physics (granting forthe moment that they are universal and necessary) explain orguarantee the universal and necessary character of the propositionsof physics proper. It is these propositions, let it be repeated, whichare relevant and important in regard to Hume's theory.

What has Kant to say on this issue? The pure faculty (i.e. ofthe understanding) of prescribing laws a priori to phenomena bymeans of mere categories, is not competent to enounce other ormore laws than those on which a nature in general, as a conform-ability to law of phenomena of space and time, depends. Particularlaws, inasmuch as they concern empirically determined phenomena,cannot be

entirelydeduced from

purelaws,

although theyall stand

under them. Experience must be superadded in order to know theseparticular laws; but in regard to experience in general, and every-thing that can be cognized as an object thereof, these a priori lawsare our only rule and guide. I In another passage he writes:2 Bynature, in the empirical sense of the word, we understand thetotality of phenomena connected in respect of their existence accord-ing to necessary rules, that is, laws. There are therefore certain laws(which are moreover a priori) which make nature possible; and all

empirical laws can exist only by means of experience, and by virtueof these primitive laws through which experience itself becomespossible. The more closely such passages as these are examinedthe more confused are they found to be; but what does seem evident,is that Kant has in view two types of law: first, primitive laws whichrender experience possible and which are presumably the trans-cendental laws of nature to which he refers in the opening of theparagraph following on the second quotation above; and second,empirical laws of nature. It appears that Kant views them in thefollowing way: empirical laws exist only by means of experiencewhich may be taken to mean that they are formulated on the basisof experience, experience itself however is possible in virtue of thetranscendental laws of nature, these in turn being derived from thea priori conceptions of the understanding, hence the empirical lawsof nature are dependent on (are derived from?) these transcendental

Critique of Pure Reason: Analytic of Conceptions, Ch. II, Sect. ii, 22., Ibid., or remarks on the three Analogies, following on Third Analogy.

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a priori proposition. To say therefore that the propositions ofempirical science are neither purely empirical nor wholly a priori is

to say that they are not wholly universal and necessary, and thatwould be to grant Hume's claim and is contrary to what Kantwished to establish. Kant asserts that there are propositions whichare without any qualification universal and necessary even thoughthey assert empirical matters.

Kant himself is not at all clear as to how the universality andnecessity come to characterize propositions of empirical cience. In thepassage quoted above he admits that particular aws cannot beentirely deduced from pure laws, although they all stand under them.

He writes alsoI that all laws of nature, without distinction, are subjectto higher principles of the understanding, inasmuch as the formerare merely applications of the latter to particular cases of experi-ence. Hence he seems to think in both these passages that theempirical law is a particular or less general case subsumed underthe universal a priori principle; and if this were so it might seem tofollow that the empirical laws of nature possessed an a priori feature,for he says2 again that even the laws of nature if they are contem-

platedas

principlesof the

empiricaluse of the

understanding possessalso a character of necessity, and we may therefore at least expectthem to be determined upon grounds which are valid a priori andantecedent to all experience. But in the first place, grave doubtexists as to what is meant by, or what is the process described by,the phrase merely applications of the latter to particular cases ofexperience and as to whether the laws of empirical science arediscovered by any process that could be so described. In the secondplace, a similar objection must be made regarding the phrase can-

not be entirely deduced from pure laws. This may or may notmean the same thing for Kant as the preceding phrase; but it isrelevant to ask what is it that is deduced and to what extent it isdeduced, if it is deduced at all. In the third place, it has alreadybeen seen that Kant distinguishes between two kinds of laws ofnature which have been labelled above as possibly being transcen-dental laws of nature and empirical aws of nature. When thereforehe refers to all laws of nature without distinction he may beunderstood to mean both transcendental laws and empirical lawsof nature. To do so, however, is to obscure the very special issuethat is in question regarding empirical laws of nature and thatarises because of the distinction between the two. In the fourthplace, when Kant speaks of laws of nature being contemplated asprinciples of the empirical use of the understanding and, as such,having a characteristic of necessity, it is difficult to see how the

Critique of Pure Reason: System of the Principles of the Pure Under-standing, Ch. II, Sect. iii. 2 Ibid.

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laws of nature he has in view can be empirical laws of physicalscience without confusing his whole theory about the synthetic a

priori principles which constitute pure physics. It is to be presumed,therefore, that he is referring to the latter or to the transcendentallaws of nature. This interpretation is confirmed by the use of thephrase all laws of nature without distinction when he wants toinclude both kinds of laws. If this is so then the a priori character-istic belongs to these transcendental laws of nature and not toempirical laws of physical science. In the following paragraph, whenmaking a distinction between empirical principles and principles ofthe pure understanding, he declares that empirical principles (thereis, it is to be admitted, the qualification merely ) have no characterof necessity how extensively valid soever they may be. Whatsignificance in this connection is to be attached to the distinctionwhich seems to be introduced by the word merely remains indoubt and a discussion of the point would require a considerableadditional space. On the other hand, he declares' that our know-ledge of the existence of things reaches as far as our perceptions,and what may be inferred from them according to empirical laws,extend. Unless such

empiricalaws have universality and

necessity,any inferences from them will not have universality and necessity,and hence our knowledge of the existence of things will not haveuniversality and necessity. Is Kant's theory itself thus subject tothe criticism which it passes on Hume?

It is clear from all this that Kant's exposition is confused andserves to confuse the reader. The fact is that he misleads as to whathe is doing and as to what he is achieving because of his varyinguse of the phrase laws of nature. He misleads, as already pointed

out, at the beginning of the Critique by declaring that physicalscience contains synthetic a priori propositions when that at mostis true (if true at all) only of a pure physics. What he is discussingare not laws of nature in any scientific sense but metaphysicalpresuppositions of scientific thought. It may be that, as is suggestedby some recent philosophico-scientific work, a distinction can bedrawn between primitive or fundamental laws of physics and otherlaws (in the more usual sense) of physics; but whether Kant'sa priori principles are anything like the former is doubtful. Even ifthe principle every event must have a cause is true and valid, thecausal laws of nature are not deducible from it and their truth isnot guaranteed by it. And it is so with Kant's other principles.There has been a long-continued belief but a mistaken one thatKant could refute Hume by showing that the principle every eventmust have a cause was synthetic a priori. The crucial point, this

The Postulates of Empirical Thought. (Just before the Refutation ofIdealism.)

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PHILOSOPHY

article has tried to argue, lies in showing that this principle guar-antees the universality and necessity of the propositions of physics

proper. When an attempt is made to consider what Kant has tosay on this crucial issue, it is found that he either ignores it or elsegets into hopeless confusion. Earlier in this article it was stated thata student of Kant was confronted with two alternatives aboutwhich he felt hesitation as to which was the correct one, namelywhether Kant accepts as a fact or proves as a conclusion that the

propositions of physics are synthetic a priori. A qualification tothis statement may now be added. It is the possibility that Kantnever takes note of the propositions of physics proper but even

when talking of laws of nature is thinking of the propositions ofpure physics.

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