Kant's Theory of Knowledge Part 20

If A and B were bodies, as they are when we apprehend the parts of a house, they could never be apprehended as successive. In other words, the process by which, on Kant's view, A and B become, and become known to be, events presupposes that they already are, and are known to be, events. Again, even if it be granted that A and B are real events, it is clear that there can be no process by which we come to apprehend them as successive. For if we apprehended events A and B separately, we could never thence advance to the apprehension of their relation, or, in other words, we could never discover which came first. Kant himself saw clearly that the perception of A followed by the perception of B does not by itself yield the perception that B follows A. In fact it was this insight which formed the starting-point of his discussion.[46] Unfortunately, instead of concluding that the apprehension of a succession is ultimate and underivable from a more primitive apprehension, he tried to formulate the nature of the process by which, starting from such a succession of perceptions, we reach the apprehension of a succession. The truth is simply that there is and can be no _process to_ the apprehension of a succession; in other words, that we do and must apprehend a real succession immediately or not at all. The same considerations can of course be supplied _mutatis mutandis_ to the apprehension of the coexistence of bodies in s.p.a.ce, e. g. of the parts of a house.

[46] Cf. B. 237, M. 144.

It may be objected that this denial of the existence of the process which Kant is trying to describe must at least be an overstatement.

For the a.s.sertion that the apprehension of a succession or of a coexistence is immediate may seem to imply that the apprehension of the course of a boat or of the shape of a house involves no process at all; yet either apprehension clearly takes time and so must involve a process. But though a process is obviously involved, it is not a process from the apprehension of what is not a succession to the apprehension of a succession, but a process from the apprehension of one succession to that of another. It is the process by which we pa.s.s from the apprehension of one part of a succession which may have, and which it is known may have, other parts to the apprehension of what is, and what is known to be, another part of the same succession.

Moreover, the a.s.sertion that the apprehension of a succession must be immediate does not imply that it may not be reached by a process. It is not inconsistent with the obvious fact that to apprehend that the boat is now turning a corner is really to apprehend that what before was going straight is now changing its course, and therefore presupposes a previous apprehension of the boat's course as straight.

It only implies that the apprehension of a succession, if reached by a process at all, is not reached by a process of which the starting-point is not itself the apprehension of a succession.

Nevertheless, a plausible defence of Kant's treatment of causality can be found, which may be formulated thus: 'Time, just as much as s.p.a.ce, is a sphere within which we have to distinguish between appearance and reality. For instance, when moving in a lift, we see, as we say, the walls moving, while the lift remains stationary. When sitting in a train which is beginning to move out of a station, we see, as we say, another train beginning to move, although it is in fact standing still. When looking at distant trees from a fast train, we see, as we say, the buildings in the intermediate s.p.a.ce moving backwards. In these cases the events seen are not real, and we only succeed in determining what is really happening, by a process which presupposes the law of causality. Thus, in the last case we only believe that the intermediate buildings do not move, by realizing that, given the uniformity of nature, belief in their motion is incompatible with what we believe on the strength of experience of these buildings on other occasions and of the rest of the world. These cases prove the existence of a process which enables us, and is required to enable us, to decide whether a given change is objective or subjective, i. e.

whether it lies in the reality apprehended or in our apprehension of it; and this process involves an appeal to causality. Kant's mistake lay in his choice of ill.u.s.trations. His ill.u.s.trations implied that the process which involves causality is one by which we distinguish a succession in the object apprehended from another relation in the object, viz. a coexistence of bodies. But he ought to have taken ill.u.s.trations which implied that the process is one by which we distinguish a succession in the object from a succession in our perception of it. In other words, the ill.u.s.trations should, like those just given, have ill.u.s.trated the process by which we distinguish an objective from a subjective change, and not a process by which we distinguish an objective change from something else also objective.

Consequently, Kant's conclusion and his _general_ method of treatment are right, even if, misled by his instances, he supports his position by arguments which are wrong.'

This defence is, however, open to the following reply: 'At first sight the cases taken undoubtedly seem to ill.u.s.trate a process in which we seek to discover whether a certain change belongs to objects or only to our apprehension of them, and in which we appeal to causality in arriving at a decision. But this is only because we ignore the relativity of motion. To take the third case: our first statement of the facts is that we saw the intermediate buildings moving, but that subsequent reflection on the results of other experience forced us to conclude that the change perceived was after all only in our apprehension and not in the things apprehended. The statement, however, that we saw the buildings moving really a.s.sumes that we, the observers, were stationary; and it states too much. What we really perceived was a relative changing of position between us, the near buildings, and the distant trees. This is a fact, and the apprehension of it, therefore, does not afterwards prove mistaken. It is equally compatible with motion on the part of the trees, or of the buildings, or of the observers, or of a combination of them; and that for which an appeal to causality is needed is the problem of deciding which of these alternatives is correct. Moreover, the perceived relative change of position is objective; it concerns the things apprehended. Hence, in this case too, it can be said that we perceive an objective succession from the beginning, and that the appeal to causality is only needed to determine something further about it. It is useless to urge that to be aware of an event is to be aware of it in all its definiteness, and that this awareness admittedly involves an appeal to causality; for it is easy to see that unless our awareness of the relative motion formed the starting-point of any subsequent process in which we appealed to the law of causality, we could never use the law to determine which body really moved.'

Two remarks may be made in conclusion. In the first place, the basis of Kant's account, viz. the view that in our apprehension of the world we advance from the apprehension of a succession of perceptions to the apprehension of objects perceived, involves a [Greek: hysteron proteron]. As Kant himself in effect urges in the _Refutation of Idealism_,[47] self-consciousness, in the sense of the consciousness of the successive process in which we apprehend the world, is plainly only attained by reflecting upon our apprehension of the world. We first apprehend the world and only by subsequent reflection become aware of our activity in apprehending it. Even if consciousness of the world must lead to, and so is in a sense inseparable from, self-consciousness, it is none the less its presupposition.

[47] Cf. p. 320.

In the second place, it seems that the true vindication of causality, like that of the first a.n.a.logy, lies in the dogmatic method which Kant rejects. It consists in insight into the fact that it is of the very nature of a physical event to be an element in a process of change undergone by a system of substances in s.p.a.ce, this process being through and through necessary in the sense that any event (i. e. the attainment of any state by a substance) is the outcome of certain preceding events (i. e. the previous attainment of certain states by it and other substances), and is similarly the condition of certain subsequent events.[48] To attain this insight, we have only to reflect upon what we really mean by a 'physical event'. The vindication can also be expressed in the form that the very _thought_ of a physical event presupposes the _thought_ of it as an element in a necessary process of change--provided, however, that no distinction is implied between the nature of a thing and what we think its nature to be. But to vindicate causality in this way is to pursue the dogmatic method; it is to argue from the nature, or, to use Kant's phrase, from the conception, of a physical event. On the other hand, it seems that the method of arguing transcendentally, or from the possibility of perceiving events, must be doomed to failure in principle. For if, as has been argued to be the case,[49] apprehension is essentially the apprehension of a reality as it exists independently of the apprehension of it, only those characteristics can be attributed to it, as characteristics which it must have if it is to be apprehended, which belong to it in its own nature or in virtue of its being what it is. It can only be because we think that a thing has some characteristic in virtue of its own nature, and so think 'dogmatically', that we can think that in apprehending it we must apprehend it as having that characteristic.[50]

[48] This statement of course includes the third a.n.a.logy.

[49] Cf. Chh. IV and VI.

[50] Cf. p. 275.

There remains to be considered Kant's proof of the third a.n.a.logy, i. e. the principle that all substances, so far as they can be perceived in s.p.a.ce as coexistent, are in thorough-going interaction.

The account is extremely confused, and it is difficult to extract from it a consistent view. We shall consider here the version added in the second edition, as being the fuller and the less unintelligible.

"Things are _coexistent_, when in empirical intuition[51] the perception[52] of the one can follow upon the perception of the other, and vice versa (which cannot occur in the temporal succession of phenomena, as we have shown in the second principle). Thus I can direct my perception first to the moon and afterwards to the earth, or conversely, first to the earth and then to the moon, and because the perceptions of these objects can reciprocally follow each other, I say that they coexist. Now coexistence is the existence of the manifold in the same time. But we cannot perceive time itself, so as to conclude from the fact that things are placed in the same time that the perceptions of them can follow each other reciprocally. The synthesis of the imagination in apprehension, therefore, would only give us each of these perceptions as existing in the subject when the other is absent and vice versa; but it would not give us that the objects are coexistent, i. e. that, if the one exists, the other also exists in the same time, and that this is necessary in order that the perceptions can follow each other reciprocally. Hence there is needed a conception-of-the-understanding[53] of the reciprocal sequence of the determinations of these things coexisting externally to one another, in order to say that the reciprocal succession of perceptions is grounded in the object, and thereby to represent the coexistence as objective. But the relation of substances in which the one contains determinations the ground of which is contained in the other is the relation of influence, and if, reciprocally, the former contains the ground of the determinations in the latter, it is the relation of community or interaction. Consequently, the coexistence of substances in s.p.a.ce cannot be known in experience otherwise than under the presupposition of their interaction; this is therefore also the condition of the possibility of things themselves as objects of experience."[54]

[51] _Anschauung._

[52] _Wahrnehmung._

[53] _Verstandesbegriff._

[54] B. 257-8, M. 156-7.

The proof begins, as we should expect, in a way parallel to that of causality. Just as Kant had apparently argued that we learn that a succession of perceptions is the perception of a sequence when we find the order of the perceptions to be irreversible, so he now definitely a.s.serts that we learn that certain perceptions are the perceptions of a coexistence of bodies in s.p.a.ce when we find that the order of the perceptions is reversible, or, to use Kant's language, that there can be a reciprocal sequence of the perceptions. This beginning, if read by itself, seems as though it should also be the end. There seems nothing more which need be said. Just as we should have expected Kant to have completed his account of the apprehension of a succession when he pointed out that it is distinguished by the irreversibility of the perceptions, so here we should expect him to have said enough when he points out that the earth and the moon are said to be coexistent because our perceptions of them can follow one another reciprocally.

The a.n.a.logy, however, has in some way to be brought in, and to this the rest of the proof is devoted. In order to consider how this is done, we must first consider the nature of the a.n.a.logy itself. Kant speaks of 'a conception-of-the-understanding of the reciprocal sequence of the determinations of things which coexist externally to one another'; and he says that 'that relation of substances in which the one contains determinations, the ground of which is contained in the other substance, is the relation of influence'. His meaning can be ill.u.s.trated thus. Suppose two bodies, A, a lump of ice, and B, a fire, close together, yet at such a distance that they can be observed in succession. Suppose that A pa.s.ses through changes of temperature a_{1} a_{2} a_{3} ... in certain times, the changes ending in states [alpha]_{1} [alpha]_{2} [alpha]_{3} ..., and that B pa.s.ses through changes of temperature b_{1} b_{2} b_{3} ... in the same times, the changes ending in states [beta]_{1} [beta]_{2} [beta]_{3}. Suppose also, as we must, that A and B interact, i. e. that A in pa.s.sing through its changes conditions the changes through which B pa.s.ses, and therefore also the states in which B ends, and vice versa, so that a_{2} and [alpha]_{2} will be the outcome not of a_{1} and [alpha]_{1} alone, but of a_{1} and [alpha]_{1}, and b_{1} and [beta]_{1} jointly.

Then we can say (1) that A and B are in the relation of influence, and also of interaction or reciprocal influence, in the sense that they _mutually_ (not alternately) determine one another's states. Again, if we first perceive A in the state [alpha]_1 by a perception A_{1}, then B in the state [beta]_{2} by a perception B_{2}, then A in the state [alpha]_{3} by a perception A_{3} and so on, we can speak (2) of a reciprocal sequence of perceptions, in the sense of a sequence of perceptions in which alternately a perception of B follows a perception of A and a perception of A follows a perception of B; for first a perception of B, viz. B_{2}, follows a perception of A, viz.

A_{1}, and then a perception of A, viz. A_{3}, follows a perception of B, viz. B_{2}. We can also speak (3) of a reciprocal sequence of the determinations of two things in the sense of a necessary succession of states which _alternately_ are states of A and of B; for [alpha]_{1}, which is perceived first, can be said to contribute to determine [beta]_{2}, which is perceived next, and [beta]_{2} can be said to contribute to determine [alpha]_{3}, which is perceived next, and so on; and this reciprocal sequence can be said to be involved in the very nature of interaction. Further, it can be said (4) that if we perceive A and B alternately, and so only in the states [alpha]_{1} [alpha]_{3} ... [beta]_{2} [beta]_{4} ... respectively, we can only fill in the blanks, i. e. discover the states [alpha]_{2} [alpha]_{4} ... [beta]_{1} [beta]_{3} ... _coexistent_ with [beta]_{2} [beta]_{4} ... and [alpha]_{1} [alpha]_{3} ... respectively, if we presuppose the thought of interaction. For it is only possible to use the observed states as a clue to the un.o.bserved states, if we presuppose that the observed states are members of a necessary succession of which the un.o.bserved states are also members and therefore have partially determined and been determined by the observed states. Hence it may be said that the determination of the un.o.bserved states coexistent with the observed states presupposes the thought of interaction.

How then does Kant advance from the a.s.sertion that the apprehension of a coexistence requires the knowledge that our _perceptions_ can be reciprocally sequent to the a.s.sertion that it presupposes the thought that the _determinations of phenomena_ are reciprocally sequent? The pa.s.sage in which the transition is effected is obscure and confused, but it is capable of interpretation as soon as we see that it is intended to run parallel to the proof of the second a.n.a.logy which is added in the second edition.[55] Kant apparently puts to himself the question, 'How are we to know when we have a reciprocal sequence of perceptions from which we can infer a coexistence in what we perceived?' and apparently answers it thus: 'Since we cannot perceive time, and therefore cannot perceive objects as dated in time with respect to one another, we cannot begin with the apprehension of the coexistence of two objects, and thence infer the possibility of reciprocal sequence in our perceptions. This being so, the synthesis of imagination in apprehension can indeed combine these perceptions [these now being really considered as determinations or states of an object perceived] in a reciprocal sequence, but there is so far no guarantee that the sequence produced by the synthesis is not an arbitrary product of the imagination, and therefore we cannot think of it as a reciprocal sequence in objects. In order to think of such a reciprocal sequence as not arbitrary but as const.i.tuting a real sequence in objects [ = 'as grounded in the object'], we must think of the states reciprocally sequent [as necessarily related and therefore]

as successive states of two coexisting substances which interact or mutually determine one another's successive states. Only then shall we be able to think of the coexistence of objects involved in the reciprocal sequence as an objective fact, and not merely as an arbitrary product of the imagination.' But, if this fairly expresses Kant's meaning, his argument is clearly vitiated by two confusions. In the first place, it confuses a subjective sequence of perceptions which are alternately perceptions of A and of B, two bodies in s.p.a.ce, with an objective sequence of perceived states of bodies, [alpha]_{1} [beta]_{2} [alpha]_{3} [beta]_{4}, which are alternately states of two bodies A and B, the same thing being regarded at once as a perception and as a state of a physical object. In the second place, mainly in consequence of the first confusion, it confuses the necessity that the perceptions of A and of B can follow one another alternately with the necessity of succession in the alternately perceived states of A and B as interacting. Moreover, there is really a change in the cases under consideration. The case with which he begins, i. e. when he is considering merely the reciprocal sequence of perceptions, is the successive perceptions of two _bodies in s.p.a.ce_ alternately, e. g. of the moon and the earth, the nature of their states at the time of perception not being in question. But the case with which he ends is the successive perception of the _states of two bodies_ alternately, e. g. of the states of the fire and of the lump of ice. Moreover, it is only in the latter case that the objective relation apprehended is that of coexistence in the proper sense, and in the sense which Kant intends throughout, viz. that of being contemporaneous in distinction from being successive. For when we say that two bodies, e. g. the moon and the earth, coexist, we should only mean that both exist, and not, as Kant means, that they are contemporaneous. For to a substance, being as it is the substratum of changes, we can ascribe no temporal predicates. That which changes cannot be said either to begin, or to end, or to exist at a certain moment of time, or, therefore, to exist contemporaneously with, or after, or before anything else; it cannot even be said to persist through a portion of time or, to use the phrase of the first a.n.a.logy, to be permanent. It will be objected that, though the cases are different, yet the transition from the one to the other is justified, for it is precisely Kant's point that the existence together of two substances in s.p.a.ce can only be discovered by consideration of their successive states under the presupposition that they mutually determine one another's states. "Besides the mere fact of existence there must be something by which A determines the place in time for B, and conversely B the place for A, because only under this condition can these substances be empirically represented as coexistent."[56] The objection, however, should be met by two considerations, each of which is of some intrinsic importance. In the first place, the apprehension of a body in s.p.a.ce in itself involves the apprehension that it exists together with all other bodies in s.p.a.ce, for the apprehension of something as spatial involves the apprehension of it as spatially related to, and therefore as existing together with, everything else which is spatial. No process, therefore, such as Kant describes is required in order that we may learn that it exists along with some other body. In the second place, that for which the principle of interaction is really required is not, as Kant supposes, the determination of the coexistence of an unperceived body with a perceived body, but the determination of that unperceived state of a body already known to exist which is coexistent with a perceived state of a perceived body. As has been pointed out, if we perceive A and B alternately in the states [alpha]_{1} [beta]_{2} [alpha]_{3} [beta]_{4} ... we need the thought of interaction to determine the nature of [beta]_{1} [alpha]_{2} [beta]_{3} [alpha]_{4} ... Thus it appears that Kant in his vindication of the third a.n.a.logy omits altogether to notice the one process which really presupposes it.

[55] B. 233-4, M. 142.

[56] B. 259, M. 157.

CHAPTER XIII

THE POSTULATES OF EMPIRICAL THOUGHT

The postulates of empirical thought, which correspond to the categories of modality, are stated as follows:

"1. That which agrees with the formal conditions of experience (according to perception and conceptions) is _possible_.

2. That which is connected with the material conditions of experience (sensation) is _actual_.

3. That of which the connexion with the actual is determined according to universal conditions of experience is _necessary_ (exists necessarily)."[1]

[1] B. 265-6, M. 161.

These principles, described as only 'explanations of the conceptions of possibility, actuality, and necessity as employed in experience', are really treated as principles by which we decide what is possible, what is actual, and what is necessary. The three conceptions involved do not, according to Kant, enlarge our knowledge of the nature of objects, but only 'express their relation to the faculty of knowledge'[2]; i. e. they only concern our ability to apprehend an object whose nature is already determined for us otherwise as at least possible, or as real, or as even necessary. Moreover, it is because these principles do not enlarge our knowledge of the nature of objects that they are called postulates; for a postulate in geometry, from which science the term is borrowed (e. g. that it is possible with a given line to describe a circle from a given point), does not augment the conception of the figure to which it relates, but only a.s.serts the possibility of the conception itself.[3] The discussion of these principles is described, contrary to the terminology adopted in the case of the preceding principles, as 'explanation' and not as 'proof'.

The discussion, however, certainly includes a proof of them, for it is Kant's main object to _prove_ that these principles const.i.tute the general character of what can be a.s.serted to be possible, actual, or necessary respectively. Again, as before, the basis of proof lies in a theory of knowledge, and in particular in Kant's theory of knowledge; for it consists in the principle that everything knowable must conform to the conditions involved in its being an object of possible experience.

[2] B. 266, M. 161. Cf. B. 286-7, M. 173-4.

[3] B. 286-7, M. 173-4.

To understand these principles and the proof of them, we must notice certain preliminary considerations. In the _first_ place, the very problem of distinguishing the possible, the actual, and the necessary presupposes the existence of distinctions which may prove open to question. It presupposes that something may be possible without being actual, and again that something may be actual without being necessary. In the _second_ place, Kant's mode of approaching the problem a.s.sumes that we can begin with a conception of an object, e. g. of a man with six toes, and then ask whether the object of it is possible, whether, if possible, it is also actual, and whether, if actual, it is also necessary. In other words, it a.s.sumes the possibility of separating what is conceived from what is possible, and therefore _a fortiori_ from what is actual,[4] and from what is necessary. _Thirdly_, in this context, as in most others, Kant in speaking of a conception is thinking, to use Locke's phraseology, not of a 'simple' conception, such as that of equality or of redness, but of a 'complex' conception, such as that of a centaur, or of a triangle in the sense of a three-sided three-angled figure. It is the apprehension of a 'complex' of elements.[5] _Fourthly_, what is said to be possible, real, or necessary is not the conception but the corresponding object. The question is not, for instance, whether the conception of a triangle or of a centaur is possible, actual, or necessary, but whether a triangle or a centaur is possible, actual, or necessary. Kant sometimes speaks loosely of conceptions as possible,[6] but the terms which he normally and, from the point of view of his theory, rightly applies to conceptions are 'objectively real' and 'fict.i.tious'.[7] _Lastly_, Kant distinguishes 'objectively real' and 'fict.i.tious' conceptions in two ways. He speaks of establishing the objective reality of a conception as consisting in establishing the possibility of a corresponding object,[8] implying therefore that a fict.i.tious conception is a conception of which the corresponding object is not known to be possible. Again, he describes as fict.i.tious new conceptions of substances, powers, and interactions, which we might form from the material offered to us by perception without borrowing from experience itself the example of their connexions, e. g. the conception of a power of the mind to perceive the future; and he says that the possibility of these conceptions (i. e. the possibility of corresponding objects) cannot, like that of the categories, be acquired _a priori_ through their being conditions on which all experience depends, but must be discovered empirically or not at all. Of such conceptions he says that, without being based upon experience and its known laws, they are arbitrary syntheses which, although they contain no contradiction, have no claim to objective reality, and therefore to the possibility of corresponding objects.[9]

He implies, therefore, that the object of a conception can be said to be possible only when the conception is the apprehension of a complex of elements together with the apprehension--which, if not _a priori_, must be based upon experience--that they are connected. Hence a conception may be regarded as 'objectively real', or as 'fict.i.tious'

according as it is the apprehension of a complex of elements accompanied by the apprehension that they are connected, or the apprehension of a complex of elements not so accompanied.

[4] The view that 'in the mere conception of a thing no sign of its existence is to be found' (B. 272, M. 165) forms, of course, the basis of Kant's criticism of the ontological argument for the existence of G.o.d. Cf. _Dialectic_, Bk. II, Ch. III, -- 4.

[5] Cf. 'a conception which includes in itself a synthesis'

(B. 267 med., M. 162 med.).

[6] E. g. B. 269 fin., M. 163 fin.; B. 270 med., M. 164 init.

The formulation which really expresses Kant's thought is to be found B. 266 med., M. 161 fin.; B. 268 init., M. 162 fin.; B. 268 med., M. 163 init.; and B. 270 med., M. 164 init.

[7] _Gedichtete._

[8] B. 268 init., M. 162 fin.

[9] B. 269-70, M. 163-4.

It is now possible to state Kant's problem more precisely. With regard to a given complex conception he wishes to determine the way in which we can answer the questions (1) 'Has the conception a possible object to correspond to it', or, in other words, 'Is the conception 'objectively real' or 'fict.i.tious'?' (2) 'Given that a corresponding object is possible, is it also real?' (3) 'Given that it is real, is it also necessary?'

The substance of Kant's answer to this problem may be stated thus: 'The most obvious guarantee of the objective reality of a conception, i. e. of the possibility of a corresponding object, is the experience of such an object. For instance, our experience of water guarantees the objective reality of the conception of a liquid which expands as it solidifies. This appeal to experience, however, takes us beyond the possibility of the object to its reality, for the experience vindicates the possibility of the object only through its reality.

Moreover, here the basis of our a.s.sertion of possibility is only empirical, whereas our aim is to discover the conceptions of which the objects can be determined _a priori_ to be possible. What then is the answer to this, the real problem? To take the case of cause and effect, we cannot reach any conclusion by the mere study of the conception of cause and effect. For although the conception of a necessary succession contains no contradiction, the necessary succession of events is a mere arbitrary synthesis as far as our thought of it is concerned; we have no direct insight into the necessity. Therefore we cannot argue from this conception to the possibility of a corresponding object, viz. a necessarily successive series of events in nature. We can, however, say that that synthesis is not arbitrary but necessary to which any object must conform, if it is to be an object of experience. From this point of view we can say that there must be a possible object corresponding to the conception of cause and effect, because only as subjected to this synthesis are there objects of experience at all. Hence, if we take this point of view, we can say generally that all spatial and temporal conceptions, as const.i.tuting the conditions of perceiving in experience, and all the categories, as const.i.tuting the conditions of conceiving in experience, must have possible objects. In other words, 'that which agrees with the formal conditions of experience (according to perception and conceptions) is _possible_'. Again, if we know that the object of a conception is possible, how are we to determine whether it is also actual? It is clear that, since we cannot advance from the mere conception, objectively real though it may be, to the reality of the corresponding object, we need perception. The case, however, where the corresponding object is directly perceived may be ignored, for it involves no inference or process of thought; the appeal is to experience alone. Therefore the question to be considered is, 'How do we determine the actuality of the object of a conception comparatively _a priori_, i. e. without direct experience of it[10]?'