Chapter II: System of All Principles of Pure Understanding (2)

This criticism is a typical illustration of Schopenhauer’s entire failure to comprehend the central thesis of Kant’s Critical idealism.[1185] The _Analytic_, so far as the main argument of its objective deduction is concerned, was to him a closed book; and as this second analogy is little else than a special application of the results of the deduction, he was equally at a loss in its interpretation. Kant was himself, of course, in large part responsible for the misunderstanding. The distinction which would seem to be implied by Kant’s language between sequence that is objective and sequence that is _merely_ subjective is completely inconsistent with Critical principles,[1186] and is as thoroughly misleading as that other distinction which he so frequently employs between the _a priori_ and the merely empirical. Schopenhauer, however, regarded these distinctions as valid, and accordingly applies them in the interpretation of Kant’s method of argument. If inner and outer experience are to be contrasted as two kinds of experience, there is, as Schopenhauer rightly insists, no sufficient ground for regarding changes due to movements of the eye as being subjective and those that are due to movements of a ship as being objective. That is not, however, Kant’s intention in the employment of these illustrations. He uses them only to make clear the fairly obvious fact that while in certain cases the order of our perceptions is subjectively initiated, in other cases we apprehend the subjective order of our experiences as corresponding to, and explicable only through, the objective sequence of events. In holding to this distinction Kant is not concerned to deny that even in the order which is determined by the subject’s purposes or caprice objective factors are likewise involved. The fact that the foundations of a house support its roof, and will therefore determine what it is that we shall apprehend when we turn the eye upwards, does not render the order of our apprehensions any the less subjective in character. But that this order is _purely_ subjective, Kant could never have asserted. His Critical principles definitely commit him to the view that even sensations and desires are integral parts of the unitary system of natural law. Kant, as we shall find, is maintaining that some such distinction between subjective and objective sequence as is illustrated in the above contrasted instances must be present from the very start of our experience--must, indeed, be constitutive of experience as such. Out of a consciousness of the purely subjective the notion of the objective can never arise.[1187] Or otherwise stated, consciousness of a time order, even though subjective, must ultimately involve the application of some non-subjective standard.

“I shall be obliged ... to derive the subjective sequence of
apprehension from the objective sequence of appearances, because
otherwise the former is entirely undetermined, and does not
distinguish any one appearance from any other.”[1188]

We interpret the subjective order in terms of an objective system; consciousness of the latter is the necessary presupposition of all awareness. It is as necessary to the interpretation of what is apprehended through the rotating eyeballs as to the apprehension of a moving ship. So far from refusing to recognise that the subjective order of our experiences is objectively conditioned, Kant is prepared to advance to the further assertion that it is only apprehensible when so conceived.

In the third _Analogy_ Kant proceeds to the connected problem, how we can apprehend the parts of a house as simultaneous notwithstanding the sequent relation of our perceptions of them, and what justification we have for thus interpreting the subjectively sequent experiences as representing objective coexistence. Just as Kant in this second _Analogy_ does not argue that irreversibility is by itself proof of causal relation, but only that the consciousness of such irreversibility demands the employment of the conception of causality, so in the third _Analogy_ he does not attempt to reduce the consciousness of coexistence to the consciousness of reversibility, but to prove that only through the application of the conception of reciprocity can the reversibility be properly interpreted. In each case the category conditions the empirical consciousness; the latter is an apprehension of determinate order only in so far as it presupposes the category. Though Kant’s treatment of the third _Analogy_ has less historical importance, and perhaps less intrinsic interest, than the proof of the second _Analogy_, it is even more significant of the kind of position which he is endeavouring to establish, and I may therefore forewarn the reader that he must not spare himself the labour of mastering its difficult, and somewhat illusive, argument. The doctrines which it expounds at once reinforce and extend the results of the second _Analogy_, while the further difficulties which it brings to view, but which it is not itself capable of meeting, indicate that the problems of the _Analytic_ call for reconsideration in the light of certain wider issues first broached in the _Dialectic_.

We may now return to Kant’s main argument. His problem, as we have found, is how consciousness of objective change, as distinguished from subjective succession, is possible. The problem, being formulated in this particular way, demands, Kant felt, careful definition of what is meant by the term ‘objective,’ upon which so much depends. To apply the illustration above used, the house as apprehended is not a thing in itself but only an appearance to the mind. What, then, do we mean by the house, as distinguished from our subjective representations of it, when that house is nothing but a complex (_Inbegriff_) of representations?[1189] The question and Kant’s answer to it are stated in subjectivist fashion, in terms of his earlier doctrine of the transcendental object. To contrast an object with the representations through which we apprehend it, is only possible if these representations stand under a rule which renders necessary their combination in some one particular way, and so distinguishes this one particular mode of representation as the only true mode from all others. The origin, therefore, of our distinction between the subjectively successive and the succession which is also objective must be due in the one case to the presence of a rule compelling us to combine the events in some particular successive order, and in the other to the absence of such a rule. Our apprehension of the house, for instance, may proceed in any order, from the roof downwards or _vice versa_, and as the order may always be reversed there is no compulsion upon the mind to regard the order of its apprehension as representing objective sequence. But since in our apprehension of an event B in time, the apprehension of B follows upon the apprehension of a previous event A, and we cannot reverse the order, the mind is compelled to view the order of succession, in terms of the category of causality, as necessitated, and therefore as objective. The order is a necessary order not in the sense that A must always precede B, that A is the cause of B, but that the order, if we are to apprehend it correctly, must in this particular case be conceived as necessary. The succession, that is, need not be conceived as a causal one, but in order to be conceived as objective succession it must be conceived as rendered necessary by connections that are causal.

Having, in this general fashion, shown the bearing of his previous analysis of objective experience upon the problem in hand, Kant proceeds to develop from it his proof of the special principle of causality. The schema of causality is necessary succession in time, and it is through this, its time aspect, that Kant approaches the principle. It has to do with the special case of _change_. To be conscious of change we must be conscious of an _event_, that is, of something as happening at a particular point in time. The change, in other words, requires to be dated, and as we are not conscious of time in general, it must be dated by reference to other events, and obviously in this case in relation to the preceding events, in contrast to which it is apprehended _as change_. But according to the results of our analysis of what constitutes objective experience, it can be fixed in its position in objective time only if it be conceived as related to the preceding events according to a necessary law; and the law of necessary connection in time is the law of causality. In order, then, that something which has taken place may be apprehended as having occurred, that is, as being an objective change, it must be apprehended as necessarily following upon that which immediately precedes it in time, _i.e._ as causally necessary.

The principle of causality thus conditions consciousness of objective succession, and Hume, in asserting that we are conscious of the succession of _events_, therefore admits all that need be assumed in order to prove the principle. The reason why Hume failed to recognise this, is that he ignored the distinction between consciousness of the subjective order of our apprehensions and consciousness of the objective sequence of events. Yet that is a distinction upon which his own position rested. For he teaches that determination of causal laws, sufficiently certain to serve the purposes alike of practical life and of natural science, can be obtained through observation of those sequences which remain constant. Such is also the position of all empiricists. They hold that causal relation is discovered by comparison of _given_ sequences. Kant’s contention is that the apprehension of change as change, and therefore ultimately the apprehension even of an arbitrarily determined order of subjective succession,[1190] presupposes, and is only possible through, an application of the category of causality. The primary function of the understanding does not consist in the clarification of our representation of an event, but in making such representation possible at all.[1191] The primary field of exercise for the understanding lies not in the realm of reflective comparison, but in the more fundamental sphere of creative synthesis.[1192] In determining the nature of the given it predetermines the principles to which all reflection upon the given must conform. The discursive activities of scientific reflection are secondary to, and conditioned by, the transcendental processes which generate the experience of ordinary consciousness. Only an experience which conforms to the causal principle can serve as foundation either for the empirical judgments of sense experience, or for that ever-increasing body of scientific knowledge into which their content is progressively translated. The principle of causality is applicable to everything experienced, for the sufficient reason that experience is itself possible only in terms of it. This conclusion finds its most emphatic and adequate statement in the _Methodology_.

“...through concepts of understanding pure reason establishes
secure principles, not however directly from concepts, but always
only indirectly through relation of these concepts to something
altogether contingent, namely, _possible experience_. For when such
experience (_i.e._ something as object of possible experience) is
presupposed, the principles are apodictically certain, though by
themselves (directly) _a priori_ they cannot even be recognised at
all. Thus no one can acquire insight into the proposition that
everything which happens has its cause, merely from the concepts
involved. It is not, therefore, a dogma, although from another
point of view, namely, from that of the sole field of its possible
employment, _i.e._ experience, it can be proved with complete
apodictic certainty. But though it needs proof, it should be
entitled a _principle_, not a _theorem_, because _it has the
peculiar character that it makes possible the very experience which
is its own ground of proof, and in this experience must always
itself be presupposed_.”[1193]

Before making further comment upon Kant’s central argument, it is advisable to consider the varying statements which Kant has given of it. We may take his successive proofs in the order in which they occur in the first edition.

=First Proof.=[1194]--The argument is developed in terms of Kant’s early doctrine of the transcendental object. The only points specially characteristic of the statement here given of that doctrine consist (_a_) in the emphasis with which it is asserted that representations can be experienced only in succession to one another, and that they can never stand in the relation of coexistence,[1195] and (_b_) in the almost complete ignoring of the transcendental object as source or ground of the rule in terms of which the successive representations are organised. (_a_) This is a point common to the arguments of all three _Analogies_. In the first and third the problem is how, from representations merely successive, permanence and coexistence can be determined. In the second _Analogy_ the problem is how from representations invariably successive a distinction can be drawn between the subjectively determined order of our apprehensions and the objective sequence of events. Or in other words: how under such conditions we can recognise an order as given, and so as prescribing the order in which it must be apprehended. Or to state the same point in still another manner: how we can distinguish between an arbitrary or reversible order and an imposed or fixed order, and so come to apprehend the subjective order of our apprehensions as in certain cases controlled by, and explicable only through, the objective sequence of events.[1196]

(_b_) The reason why the transcendental object, as source of the determinate and prescribed order of the given events, falls into the background in this passage is that Kant is concerned only with the general principle or category by means of which the order is apprehended as necessary. That principle has a subjective origin even though the particular sequences of concrete events have by means of that concept to be conceived as inexorably determined by their noumenal conditions.[1197] The principle accounts for the _comprehension_ of the order as objective, and that is the only point with which Kant is here immediately concerned. That the assertion of the subjective origin of the category is not inconsistent with recognition of the imposed order of the given has already been shown above.[1198] Kant’s own illustration, in this section, of the ship sailing down stream shows that he was prepared to assume without question that they are compatible. His argument is, however, obscure, owing to his failure to distinguish between the two senses in which the term ‘rule’ may be employed. The term may signify either the universal and merely formal principle that every event must have a cause, or it may be used to denote the fixed order in which concrete events are presented to sense-perception. The latter order need not represent a series the members of which are causally connected _with one another_, but only one that is due to causal necessities. Thus the successive positions of a ship sailing down stream are not interrelated as cause and effect, and yet in order to be apprehended as objectively successive must be conceived as causally conditioned. The term ‘rule’ has very different meanings in the two cases. ‘Rule’ in the first sense is of subjective origin. It is _formal_, and can never be given. It is read into the given. ‘Rule’ in the second sense is given merely, and being due to noumenal conditions constitutes the _material_ element in natural science, the empirical content of some particular causal law. Owing to Kant’s failure explicitly to distinguish between these two very different connotations of the term, such a sentence as the following is ambiguous: “That in appearance which contains the condition of this necessary rule of apprehension is the object.” Kant may mean that the prescribed order of the concrete events is due to the transcendental object; but in that case it is not given as _necessary_. Necessity, as he constantly insists, is the one thing that can never be given. The sentence is also misleading through its use of the term ‘appearance.’ That term has no legitimate place in a passage inspired by the doctrine of the transcendental object; there can be no such middle term between subjective representations and the thing in itself. As Kant himself states,[1199] appearance defined in terms of that doctrine is “nothing save a complex of representations.”

There is a very essential difference in the view which Kant takes of the causal relation according as he is proceeding upon subjectivist or upon phenomenalist lines. From the one point of view appearances are representations merely, and accordingly are entirely devoid of causal efficacy. They are not causes and effects of one another. They have not the independence or self-persistence necessary for the exercise of dynamical energy or even for the reception of modifications. Being “states of the identical self,” all causal relation, dynamically conceived, must lie solely in their noumenal conditions. Causality reduces to the thought of necessitated (not necessitating) sequence. It is, as Kant has suggested in A 181 = B 224, a mere ‘analogy’ in terms of which we apply the logical relation of ground and consequence[1200] to the interpretation of our subjective representations, and so view them as grounded not in one another but exclusively in the thing in itself. Causality in the strict sense, _i.e._ dynamical agency, can be looked for only in the noumenal sphere.

Caird, while adopting this explanation of the term ‘analogy,’[1201] is, as might be expected from his Hegelian standpoint, extremely indefinite and non-committal as to whether or not empirical objects can be genuine causes. Riehl, notwithstanding his professedly realistic interpretation of Kant, adopts the above subjectivist view of natural causation. So also do Benno Erdmann and Paulsen. The latter[1202] speaks with no uncertain voice.

“Causality in the phenomenal world signifies for Kant, as for Hume,
nothing but regularity in the sequence of phenomena. Real causal
efficiency cannot of course occur here, for phenomena are
ideational products. As such they can no more produce an effect
than concepts can.”

The corresponding phenomenalist view of the causal relation receives no quite definite formulation either in this section or elsewhere in the _Critique_, but may be gathered from the general trend of Kant’s phenomenalist teaching.[1203] It is somewhat as follows. The term ‘analogy’ is viewed as having a meaning very different from that above suggested. The causal relation is not a mere analogy from the logical relation of ground and consequence; it is the representation of genuinely dynamical activities in the objects apprehended. Those objects are not mere states of the self, subjective representations. They are part of an independent order which in the form known to us is a phenomenalist transcript of a deeper reality. If the causal relation is the analogy of anything distinguishable from itself, it is an analogon or interpretation of dynamical powers exercised by things in themselves,[1204] not of the merely logical relation between premisses and conclusion. The objects of representation may exercise powers which representations as such can never be conceived as possessing. Between the individual’s subjective states and things in themselves stands the phenomenal world of the natural sciences. Its function, whether as directly experienced through sense-perception or as conceptually reconstructed through scientific hypothesis, is to stand as the representative in human consciousness of that noumenal realm in which all existence is ultimately rooted. The causal interactions of material bodies in space are as essentially constitutive of those bodies as are any of their quantitative properties. Causal relation, even in the phenomenal sphere, must not be identified with mere conformity to law. The true and complete purpose of the natural sciences is not to be found in the Berkeleian or sceptical ideal of simplification, but in the older and sounder conception of causal explanation. That, at least, is the view which Kant invariably defends whenever he has occasion to discuss the principles of physical science.

=Second Proof.=[1205]--The argument of the first proof is here developed in indirect fashion. In the _absence_ of any rule prescribing necessary sequence, no distinction can be made between subjective and objective succession. The justification for such a rule lies therefore, not in an inductive inference from repeated experience, but in its necessity for the possibility of experience. It is an expression of the synthetic unity in which experience consists.

=Third Proof.=[1206]--This is for the most part merely a restatement of the first proof. It differs from it in making rather more explicit that the objective reference involved in the notion of the transcendental object is one that carries the mind beyond all representations to the thought of something which determines their order according to a rule. Otherwise the ambiguities of the terms employed are identical with those of the first proof. Its concluding paragraph, however, is a much clearer statement of the difficult argument of A 192-3 = B 238-9.

=Fourth Proof.=[1207]--This proof differs from all the others. It argues from the characteristics of pure time to the properties necessary to the empirical representation of the time-series. As time cannot be experienced in and by itself, all its essential characteristics must be capable of being represented in terms of appearance. “Only in appearances can we empirically recognise continuity in the connection of times.” The primary function of the understanding is to make such recognition possible, and it does so by “transferring the time order to the appearances and their existence.” It is a necessary law of time that we can only advance to the succeeding through the preceding. Each moment of time is the indispensable condition of the existence of that which follows it. We can pass to the year 1915 only by way of the preceding year 1914. And since, as just noted, time is not cognisable by itself but only as the form of our perceptions, this law must be applicable to them. We can only be conscious of all times as successively conditioning one another in one single time, and that means in one single _objective_ time, if we are conscious of all the phenomena perceived as conditioning one another in their order in time.

It is somewhat difficult to understand how Kant came to formulate the argument in this form. The explanation may perhaps be found in his preoccupation[1208] with the doctrine of a transcendental activity of the productive imagination and with the connected doctrine of a pure _a priori_ manifold. For this proof would seem to rest upon the assumption that the characteristics of time are known purely _a priori_ and therefore with complete certainty, independently of sense experience. The unusual and somewhat scholastic character of the proof also appears in Kant’s substitution of the principle of sufficient reason for the principle of causality. But despite the artificial character of the standpoint, the argument serves to bring prominently forward Kant’s central thesis, viz. that the principle of causality is presupposed in all consciousness of time, even of the subjectively successive. Also, by emphasising that time in and by itself can never be “an object of perception,” and that the relating of appearances to “absolute time” is possible only through the determining of them in their relations to one another, it supplies the data for correction of its own starting-point.

=Fifth Proof.=[1209]--This proof is probably later than the preceding proofs. Though its essential content coincides with that of the opening proof, its formulation would seem to be a first attempt at statement of the sixth proof, _i.e._ of the argument which Kant added in the second edition. Adickes considers this proof to be earlier in date than the first four proofs, but the reason which he assigns for so regarding it, viz. that Kant here postulates a synthesis of the imagination independent of the categories as preceding a synthesis of apprehension in terms of the categories, seems to be based upon a much too literal reading of Kant’s loose mode of statement. The argument rather appears to be, as in the sixth proof, that synthesis of the imagination may be either subjective or objective; and the term “apprehension” would seem to be used as signifying that the manifold synthesised is _given_ to the imagination through actual sense experience, and that as thus given it has a determinate order of its own. The argument concludes with the statement (more definite than any to be found in the preceding arguments), that the proof of the principle of causality consists in its indispensableness as a condition of all empirical judgments, and so of experience as such. As a ground of the possibility of experience it must be valid of all the objects of experience.

=Sixth Proof.=[1210]--The argument of the fifth proof is here more clearly stated. All synthesis is due to “the faculty of imagination which determines inner sense in respect of the time relation.” Such synthesis may, however, yield the consciousness either of subjective succession or of succession “in the object.” In the latter form it presupposes the employment of a pure concept of the understanding, that of the relation of cause and effect. And the conclusion reached is again that only so is empirical knowledge possible. This mode of stating the argument is far from satisfactory. It tends to obscure Kant’s central thesis, that only through consciousness of an objective order is consciousness of subjective sequence possible, and that the principle of causality is therefore a conditioning factor of all consciousness. The misleading distinction drawn in the _Prolegomena_ between judgments of perception and judgments of experience also crops out in Kant’s use of the phrase “mere perception.”[1211]

* * * * *

We may again return to Kant’s central argument. For we have still to consider certain objections to which it may seem to lie open, and also to comment upon Kant’s further explanations in the remaining paragraphs of the section.[1212] Kant’s imperfect statement of his position has suggested to Hutchison Stirling and others a problem which is largely artificial, namely, how the mind is enabled to recognise the proper occasions upon which to apply the category of causality. On the one hand sequence as such cannot be the criterion, since many sequences are not causal, and on the other hand the absence of sequence does not appear to debar its application, since cause and effect would frequently seem to be co-existent. This difficulty arises from failure to appreciate the central thesis upon which Kant’s proof of the principle of causality ultimately rests. Kant’s diffuse and varying mode of statement may conceal but never conflicts with that thesis, which consists in the contention that the category of causality is a necessary and invariable factor in all consciousness. Nothing can be apprehended save in terms of it.[1213] It prescribes an interpretation which the mind has no option save to apply in the consciousness of each and every event, of the coexistent no less than of the sequent. Whether two changes are coexistent or are successive, each must be conceived as possessing an antecedent cause. The only difference is that in the case of sequent events one of them (_i.e._ the antecedent change) may, upon empirical investigation, be found to be itself the cause of the second and subsequent event, whereas with coexistent events this can never be possible. As the principle of causality is that every event must have an antecedent cause, it follows that where there is no sequence there can be no causation. But when Kant states that sequence is “the sole empirical criterion”[1214] of the causal relation, he does less than justice to the position he is defending. The empirical criteria are manifold in number, and are such as John Stuart Mill has attempted to formulate in his inductive methods.

Schopenhauer has objected[1215] that Kant’s argument proves too much, since it would involve that all objective sequences, such as that of night and day or of the notes in a piece of music, are themselves causal sequences. This criticism has been replied to by Stadler[1216] in the following terms:

“When Schopenhauer adduces the sequence of musical notes or of day
and night, as objective sequences which can be known without the
causal law, we need only meet him with the question, Where in these
cases is the substance that changes? So soon as he is forced to put
his objection into the form required to bring it into relation to
the question of the possibility of knowledge, his error becomes
obvious. His instances must then be expressed thus:--The instrument
passes from one state of sound into another; the earth changes from
the measure of enlightenment which makes day, to that which makes
night. Of such changes no one will say that they are not referred
to a cause. And we may quote in this reference the appropriate
saying of Kant himself, ‘Days are, as it were, the children of
Time, since the following day with that which it contains is the
product of the previous day.’”

Night and day, in so far as they are sequent events, must be conceived in terms of causality, not in the sense that night causes day, but as being determined by causes that account not only for each separately, but also for the alternating sequence of the one upon the other. Such causes are found by the astronomer to lie in the changing positions of the earth relatively to the sun.

Schopenhauer adds a further objection of a more subtle nature, which has again been excellently stated and answered by Stadler:

“Schopenhauer points out that what we call chance is just a
sequence of events which do not stand in causal connexion. ‘I come
out of the house and a tile falls from the roof which strikes me;
in such a case there is no causal connexion between the falling of
the tile and my coming out of the house, yet the succession of
these two events is objectively determined in my apprehension of
them.’ How have we to criticise this case from the transcendental
point of view? We know that successions become necessary, _i.e._
objective, for our consciousness, when we regard them as changes of
a substance which are determined by a cause. But it is shown here
that there are successions in which the single members are changes
of different substances. If substance S changes its state A into B
on account of the cause X, and substance S´ changes its state A´
into B´ on account of the cause X´, and if I call the first change
V and the second V´, the question arises how the objectivity of the
succession V V´ is related to the law of causality. Sequences such
as V V´ are very frequent, and our consciousness of the objectivity
is certain. Do we owe this consciousness to the same rule as holds
good in other cases? Certainly. The distinction is not qualitative,
but rests only on the greater complication of the change in
question. The sequence V V´ can become objective only if I think it
as a necessary connexion. It must be so determined that V can only
follow V´ in ‘consciousness in general’; there must be a U, the
introduction of which is the cause that V´ follows V. To be
convinced of this, I do not need actually to know U. I know that on
every occasion U causes the succession V V´. Of course, this
presupposes that all data of the states considered, A and A´,
remain identical. But whether these data are very simple or
endlessly complex, whether they are likely to combine to the given
result frequently or seldom, is indifferent for the objectifying of
the event; it is not the perception of U, but the presupposition of
it, which makes the change necessary and so objective for
us.”[1217]

To turn now to the other difficulty which Kant himself raises in A 202-3 = B 247-8, viz. that cause and effect would frequently seem to be coexistent, and the “sole empirical criterion” to be therefore absent. It may from this point of view be maintained that the great majority of causes occur simultaneously with their effects, and that such time sequence as occurs is due solely to the fact that the cause cannot execute itself in one single instant. Kant has little difficulty in disposing of this objection. Causality concerns only the _order_, not the _lapse_, of time; and the sequence relation must remain even though there is no interval between the two events. If a leaden ball lies upon a cushion it makes a depression in it. The ball and the depression are coexistent. None the less, when viewed in their dynamical relation, the latter must be regarded as sequent upon the former. If the leaden ball is placed upon a smooth cushion a hollow is at once made, but if a hollow exists in a cushion a ball need not appear. In other words, the criteria for the determination of specific causal relations are neither the presence nor the absence of sequence, but are empirical considerations verifiable only upon special investigation.[1218] The observer is called upon to disentangle the complicated web of given appearances under the guidance of the quite general and formal principle that every event is due to some antecedent cause. He must do so as best he can through the application of his acquired insight, and, when necessary, by means of the requisite experimental variation of conditions.

In the two following paragraphs (A 204-5 = B 249-51) Kant raises points which he later discussed more fully in the _Metaphysical First Principles of Natural Science_.[1219] As adequate explanation of the argument would be a very lengthy matter, and not of any very real importance for the understanding of the general Critical position, we may omit all treatment of it. In the sections of the _Metaphysical First Principles_ just cited, the reader will find the necessary comment and explanation. Such bearing as these two paragraphs have upon Kant’s view of the nature of the causal relation has been noted above.[1220]

In the section on _Anticipations of Perception_[1221] Kant has stated that the principle of the continuity of change involves empirical factors, and therefore falls outside the limits of transcendental philosophy. To this more correct attitude Kant, unfortunately, did not hold. In A 207-11 = B 252-6 he professes to establish the principle in _a priori_ transcendental fashion as a necessary consequence of the nature of time. This proof is indeed thrice repeated with unessential variations, thereby clearly showing that these paragraphs also are of composite origin. The argument in all three cases consists in inferring from the continuity of time the continuity of all changes in time. As the parts of time are themselves times, of which no one is the smallest, so in all generation in time, the cause must in its action pass through all the degrees of quantity from zero to that of the final effect.

“Every change has a cause which evinces its causality in the whole
time in which the change takes place. This cause, therefore, does
not engender the change suddenly (at once or in one moment), but in
a time, so that, as the time increases from its initial moment _a_
to its completion in _b_, the quantity of the reality (_b-a_) is in
like manner generated through all lesser degrees which are
contained between the first and the last.”[1222]

This argument is inconclusive. As Kant himself recognises in regard to space,[1223] we may not without special proof assume that what is true of time must be true of the contents of time. If time, change, and causation can be equated, what is true of one will be true of all three. But the assumption upon which the argument thus rests has not itself been substantiated.

In the third proof[1224] the argument is stated in extreme subjectivist terms which involve the further assumption that what is true of apprehension is _ipso facto_ true of everything apprehended. The possibility of establishing the law of dynamical continuity follows, Kant declares, as a consequence of its being a law of our subjective apprehension.

“We anticipate only our own apprehension, the formal condition of
which, inasmuch as it inheres in the mind prior to all given
appearances, must certainly be capable of being known _a
priori_.”[1225]

Kant’s attitude towards the physical principle of continuity underwent considerable change. In his _New Doctrine of Motion and Rest_ (1758)[1226] he maintains that it cannot be proved, and that physicists may rightly refuse to recognise it even as an hypothesis. It is in the Essay on _Negative Quantity_ (1763)[1227] that Kant first adopts the attitude of the _Critique_, and rejects the “speculative” objections raised against the mathematical conception of the infinitely small. In the _Metaphysical First Principles of Natural Science_[1228] the principle of continuity is defended and developed, but only in its application to material existence, not in its relation to the causal process.

C. =Third Analogy.=--_All substances, in so far as they are coexistent, stand in thoroughgoing communion,[1229] i.e. in reciprocity with one another._ Or, as in the second edition: _All substances, so far as they can be perceived to coexist in space, are in thoroughgoing reciprocity._

This section contains four separate proofs. The first three paragraphs in the text of the first edition contain the first proof. The fourth paragraph supplies a second proof, and the fifth paragraph a third. In the second edition Kant adds a fourth proof (the first paragraph of the text of the second edition).

We may lead up to these proofs by first formulating (_a_) the fundamental assumption upon which they proceed, and (_b_) the thesis which they profess to establish. (_a_) The argument involves the same initial assumption as the preceding _Analogies_, viz. that representations exist exclusively in succession, or stated in phenomenalist terms, that the objectively coexistent can be apprehended only in and through representations that are sequent to one another in time.[1230] Upon this assumption the problem of the third _Analogy_ is to explain how from representations all of which are in succession we can determine the objectively coexistent. (_b_) In the _Dissertation_[1231] Kant had maintained that though the possibility of dynamical communion of substances is not necessarily involved in their mere existence, such interaction may be assumed as a consequence of their common origin in, and dependence upon, a Divine Being. In the _Critique_ no such metaphysical speculations are any longer in order, and Kant recognises that as regards things in themselves it is not possible to decide whether dynamical interaction is, or is not, necessarily involved in coexistence. The problem of this third _Analogy_ concerns only appearances, which as such must be subject to the conditions of unitary experience; and one such condition is that they be apprehended as belonging to a single objective order of nature, and therefore as standing in reciprocal relations of interaction. _The apprehension of substances as reciprocally determining one another is_, Kant contends, _an indispensable condition of their being known even as coexistent_. Such is Kant’s thesis. The proof may first be stated in what may be called its typical or generic form. Kant’s four successive proofs can then be related to it as to a common standard.

Two things, A and B, can be apprehended as coexistent only in so far as we can experience them in either order, _i.e._ when the order of our perceptions of them is reversible. If they existed in succession, this could never be possible. The earlier member of a time series is past when the succeeding member is present, and what belongs to the past can never be an object of perception. The fact that the order in which things can be perceived is reversible would thus seem to prove that they do not exist successively to one another in time.[1232] That, however, is not the case. By itself such experience does not really suffice to yield consciousness of coexistence. It can yield only consciousness of an alternating succession.[1233] A further factor, namely, interpretation of the reversibility of our perceptions as due to their being conditioned by objects which stand in the relation of reciprocal determination, must first be postulated. If these objects mutually determine one another to be what they are, no one of them can be antecedent to or subsequent upon the others; and by their mutual reference each will date the others as simultaneous with itself. In other words, the perception of the coexistence of objects involves the conception of them as mutually determining one another. The principle of communion or reciprocity conditions the experience of coexistence, and is therefore valid for objects apprehended in that manner.

Kant also maintains, more by implication than by explicit statement, that as A and B need not stand in any direct relation, the apprehension of them as coexistent involves the conception of an all-embracing order of nature within which they fall and which determines them to be what they are. If any one of them, even the most minute and insignificant, were conceived as altered, corresponding simultaneous variations would have to be postulated for all the others. The unity of the phenomenal world is the counterpart of the unity of apperception. Unity of experience involves principles which prescribe a corresponding unity in the natural realm. Dynamical _communion_ is the sufficient and necessary fulfilment of this demand. It carries to completion the unity demanded by the preceding _Analogies_ of _substance_ and _causality_. Kant sums up his position in a note to A 218 = B 265.

“The unity of the world-whole, in which all appearances have to be
connected, is evidently a mere consequence of the tacitly assumed
principle of the communion of all substances which are coexistent.
For if they were isolated, they would not as parts constitute a
whole. And if their coexistence alone did not necessitate their
connection (the reciprocal action of the manifold) we could not
argue from the former, which is a merely ideal relation, to the
latter, which is a real relation. We have, however, in the proper
context, shown that communion is really the ground of the
possibility of an empirical knowledge of coexistence, and that
therefore the actual inference is merely from this empirical
knowledge to communion as its condition.”

To turn now to Kant’s successive proofs. The first[1234] calls for no special comment. It coincides with the above. The second[1235] proof is an incompletely stated argument, which differs from the first only in its more concrete statement of the main thesis and in its limitation of the argument to spatial existences. Dynamical community is the indispensable condition of our apprehension of any merely spatial side-by-sideness. Kant now adds that it is the dynamical continuity of the _spatial_ world which enables us to apprehend the coexistence of its constituents. The important bearing of this argument we shall consider in its connection with the proof which Kant added in the second edition.

The third[1236] proof is probably the earliest in date of writing. It draws a misleading distinction between subjective and objective coexistence, and seems to argue that only the latter form of coexistence need presuppose the employment of the category of reciprocity. That runs directly counter to the central thesis of the other proofs, that only in terms of dynamical relation is coexistence at all apprehensible. That the above distinction indicates an early date of writing would seem to be confirmed by the obscure phrase “community of apperception” which is reminiscent of the prominence given to apperception in Kant’s earlier views, and by the concluding sentence in which Kant employs terms--inherence, consequence, and composition--that are also characteristic of the earlier stages of his Critical enquiries.[1237]

It is significant that in the new argument[1238] of the second edition the space factor, emphasised in the second proof of the first edition, is again made prominent.[1239] The principle is, indeed, reformulated in such manner as to suggest its limitation to spatial existences. “All substances, so far as they can be perceived to coexist _in space_, are in thoroughgoing reciprocity.” Now it is decidedly doubtful whether Kant means to limit the category of reciprocity to spatial existences. As we have already noted,[1240] he would seem to hold that though the category of causality can _acquire_ meaning only in its application to events in space, it may in its subsequent employment be extended to the states of inner sense. The latter are effects dynamically caused, and among their causal conditions are mechanical processes in space. The extension of the category of reciprocity to include sensations and desires undoubtedly gives rise to much greater difficulties than those involved in the universal application of the causal principle. On the other hand, its limitation to material bodies must render the co-ordination of mental states and mechanical processes highly doubtful, and would carry with it all the difficulties of an epiphenomenal view of psychical existences. The truth probably is that in this matter Kant had not thought out his position in any quite definite manner; and that owing to the influence, on the one hand of the dualistic teaching of the traditional Cartesian physics, and on the other of his increasing appreciation of the part which space must play in the definition and proof of the principles of understanding, he limited the category of reciprocity to spatial existences, without considering how far such procedure is capable of being reconciled with his determinist view of the empirical self. His procedure is also open to a second objection, namely, that while thus reformulating the principle, he fails to remodel his proof in a sufficiently thoroughgoing fashion. The chief stress is still laid upon the temporal element; and in order to obtain a proof of the principle that will harmonise with the prominence given to the space-factor, we are thrown back upon such supplementary suggestions as we can extract from the second argument of the first edition. It is there stated that “without dynamical communion even spatial community (_communio spatii_) could never be known empirically.”[1241] That is an assertion which, if true, will yield a proof of the principle of reciprocity analogous to that which has been given of the principle of causality; for it will show that just as the conception of causality is involved in, and makes possible, the awareness of time, so the conception of reciprocity is involved in, and makes possible, the awareness of space.

The proof will be as follows. The parts of space have to be conceived as spatially interrelated. Space is not a collection of independent spaces; particular spaces exist only in and through the spaces which enclose them. In other words, the parts of space mutually condition one another. Each part exists only in and through its relations, direct or indirect, to all the others; the awareness of their coexistence involves the awareness of this reciprocal determination. But space cannot, any more than time, be known in and by itself;[1242] and what is true of space must therefore hold of the contents, in terms of the interrelations of which space can alone be experienced. How, then, can the reciprocal determination of substances in space be apprehended by a consciousness which is subject in all its experiences to the conditions of time? As Kant has pointed out in A 211 = B 258,[1243] objective coexistence is distinguished from objective sequence by reversibility of the perceptions through which it is apprehended. When A and B coexist, our perceptions can begin with A and pass to B, or start from B and proceed to A. There is also, as Kant observes in the second proof, a further condition, namely, that the transition is in each case made through a _continuous_ series of changing perceptions.

“Only the continuous influences in all parts of space can lead our
senses from one object to another. The light, which plays between
our eye and the celestial bodies, produces a mediate communion
between us and them, and thereby establishes the coexistence of the
latter. We cannot empirically change our position (perceive such a
change), unless matter in all parts of space makes the perception
of our position possible to us. Only by means of its reciprocal
influence can matter establish the simultaneous existence of its
parts, and thereby, though only mediately, their coexistence with
even the most remote objects. Without communion, every perception
of an appearance in space is broken off from every other, and the
chain of empirical representations, _i.e._ experience, would have
to begin entirely anew with every new object, without the least
connection with preceding representations, and without standing to
them in any relation of time.”[1244]

But even such reversibility of _continuous_ series does not by itself establish coexistence. For in the imagination[1245] we can represent such series, without thereby acquiring the right to assert that they exist not as series but as simultaneous wholes. And as Kant might also have pointed out, even in sense-perception we can experience reversible continuous series that do not in any way justify the inference to coexistence. We may, for instance, produce on a musical instrument a series of continuously changing sounds, and then in immediate succession produce the same series in reverse order. An additional factor is therefore required, namely, the interpretation of the reversibility of our perceptions as being grounded in objects which, because spatially extended, and spatially continuous with one another, can yield continuous series of perceptions, and which, because of their thoroughgoing reciprocity, make possible the reversing of these series. To summarise the argument in a sentence: as the objectively coexistent, if it is to be known at all, can only be known through sequent representations, the condition of its apprehension is the possibility of interpreting reversible continuous series as due to the reciprocal interaction of spatially ordered substances.

This argument has a twofold bearing. Its most obvious consequence is that all things apprehended as coexistent must be conceived as standing in relations of reciprocal interaction; but by implication this involves the further consequence that the conceptual principle of reciprocity is an integral factor in all apprehension of space. Space, though intuitive in character, has a meaning that demands this concept for its articulation. Just as consciousness of temporal sequence is only possible in terms of causation, so consciousness of spatial coexistence is only possible through application of the category of reciprocity. And since, on Kant’s view, awareness of space conditions awareness of time, these conclusions carry the Critical analysis of our consciousness of time a stage further. In confirmation of the more general argument of the objective deduction, reciprocity is added to the already large sum-total of the indispensable conditions of our time-consciousness; while in regard to time itself it is shown that, owing to its space-reference, coexistence may be counted among its possible modes.

I have made occasional reference to the positions adopted by Stout in his _Manual of Psychology_, and may here indicate their relation to the present argument. Stout cites four “categories” or ultimate principles of unity which “belong even to rudimentary perceptual consciousness as a condition of its further development,”[1246] namely, spatial unity, temporal unity, causal unity, and the unity of different attributes as belonging to the same thing. The criticism which, from the standpoint of the _Analogies_, has to be passed upon this list,[1247] is that it ignores the category of reciprocity, _i.e._ of systematic interconnection, and that it fails to recognise the close relation in which the various principles stand to one another. The temporal unity must not be isolated from causal unity, nor either of them from the spatial unity, with which the category of reciprocity is inseparably bound up. Further, Kant maintains that these principles are demanded, not merely for the _development_ of perceptual consciousness, but for its very existence.

But Kant’s argument suggests many difficulties which we have not yet considered, and we may again employ Schopenhauer’s criticisms to define the issues involved.

“The conception of reciprocity ought to be banished from
metaphysics. For I now intend, quite seriously, to prove that there
is no reciprocity in the strict sense, and this conception, which
people are so fond of using, just on account of the indefiniteness
of the thought, is seen, if more closely considered, to be empty,
false, and invalid.... It implies that both the states A and B are
cause and that both are effect of each other; but this really
amounts to saying that each of the two is the earlier and also the
later; thus it is an absurdity.”[1248]

This criticism proceeds on the assumption that the category of reciprocity reduces to a dual application of the category of causality. If that were the case, there would, of course, be no separate category of reciprocity,[1249] and further it would, as Schopenhauer maintains, be impossible to regard A and B as being at one and the same time both cause and effect of one another. Causality determines the order of the states of substances in the time series; reciprocity must be distinct from causality if it is to be capable of defining the order of their coexistent states in space. A deduction from the dual application of the conception of causality has, therefore, no bearing upon the question of the possibility of this further category. Kant has laid himself open to this criticism by a passage which occurs in the first proof, and which shows that he was not quite clear in his own mind as to how reciprocity ought to be conceived.

“That alone can determine the position of anything else in time,
which is its cause or the cause of its determinations. Every
substance (inasmuch as only in its determinations can it be an
effect) must therefore contain in itself the causality of certain
determinations in the other substance, and at the same time the
effects of the causality of that other, _i.e._ they must stand in
dynamical communion (immediately or mediately), if their
coexistence is to be known in any possible experience.”[1250]

It should be noted that in the new proof[1251] in the second edition Kant is careful to employ the terms ground and influence in place of the terms cause and causality.