The answer must be that we do so by finding it to be "connected with an actual perception in accordance with the a.n.a.logies of experience"[11]. For instance, we must establish the actuality of an object corresponding to the conception of a volcanic eruption by showing it to be involved, in accordance with the a.n.a.logies (and with particular empirical laws), in the state of a place which we are now perceiving. In other words, we can say that "that which is connected with the material conditions of existence (sensation) is _actual_".
Finally, since we cannot learn the existence of any object of experience wholly _a priori_, but only relatively to another existence already given, the necessity of the existence of an object can never be known from conceptions, but only from its connexion with what is perceived; this necessity, however, is not the necessity of the existence of a substance, but only the necessity of connexion of an un.o.bserved state of a substance with some observed state of a substance. Therefore we can (and indeed must) say of an un.o.bserved object corresponding to a conception, not only that it is real, but also that it is necessary, when we know it to be connected with a perceived reality "according to universal conditions of experience"; but the necessity can be attributed only to states of substances and not to substances themselves."
[10] Cf. B. 279, M. 169 and p. 4, note 1.
[11] B. 273, M. 165.
Throughout this account there runs one fatal mistake, that of supposing that we can separate our knowledge of things as possible, as actual, and as necessary. Even if this supposition be tenable in certain cases,[12] it is not tenable in respect of the objects of a complex conception, with which Kant is dealing. If we know the object of a complex conception to be possible, we already know it to be actual, and if we know it to be actual, we already know it to be necessary. A complex conception in the proper sense is the apprehension of a complex of elements together with the apprehension of, or insight into, their connexion.[13] Thus, in the case of the conception of a triangle we see that the possession of three sides necessitates the possession of three angles. From such a conception must be distinguished Kant"s "fict.i.tious" conception, i. e. the apprehension of a complex of elements without the apprehension of connexion between them. Thus, in the case of the conception of a man with six toes, there is no apprehension of connexion between the possession of the characteristics indicated by the term "man" and the possession of six toes. In such a case, since we do not apprehend any connexion between the elements, we do not really "conceive" or "think"
the object in question, e. g. a man with six toes. Now in the case of a complex conception proper, it is impossible to think of a corresponding individual as only possible. The question "Is a triangle, in the sense of a figure with three sides and three angles, possible?" really means "Is it possible for a three-sided figure to have three angles?" To this question we can only answer that we see that a three-sided figure can have three angles, because we see that it must have, and therefore has, and can have, three angles; in other words, that we see a triangle in the sense in question to be possible, because we see it to be necessary, and, therefore, actual, and possible. It cannot be argued that our insight is limited to the fact that if there are three-sided figures they must be three-angled, and that therefore we only know a triangle in the sense in question to be possible. Our apprehension of the fact that the possession of three sides necessitates the possession of three angles presupposes knowledge of the existence of three-sided figures, for it is only in an actual three-sided figure that we can apprehend the necessity. It may, however, be objected that the question ought to mean simply "Is a three-sided figure possible?" and that, understood in this sense, it cannot be answered in a similar way. Nevertheless, a similar answer is the right answer. For the question "Is a three-sided figure possible?"
really means "Is it possible for three straight lines to form a figure, i. e. to enclose a s.p.a.ce?" and we can only answer it for ourselves by seeing that a group of three straight lines or directions, no two of which are parallel, must, as such, enclose a s.p.a.ce, this insight presupposing the apprehension of an actual group of three straight lines. It may be said, therefore, that we can only determine the possibility of the object of a complex conception in the proper sense, through an act in which we apprehend its necessity and its actuality at once. It is only where conceptions are "fict.i.tious", and so not properly conceptions, that appeal to experience is necessary. The question "Is an object corresponding to the conception of a man with six toes possible?" presupposes the reality of man and asks whether any man can have six toes. If we understood the nature of man and could thereby apprehend either that the possession of six toes was, or that it was not, involved in one of the possible differentiations of man, we could decide the question of possibility _a priori_, i. e. through our conceiving alone without an appeal to experience; but we could do so only because we apprehended either that a certain kind of man with six toes was necessary and actual, or that such a man was impossible and not actual. If, however, as is the case, we do not understand the nature of man, we can only decide the question of possibility by an appeal to experience, i. e.
to the experience of a corresponding object, or of an object from which the existence of such an object could be inferred. Here, therefore--a.s.suming the required experience to be forthcoming--we can appeal to Kant"s formula and say that we know that such a man, i. e. an object corresponding to the conception, is actual, as being connected with the material conditions of experience. But the perception which const.i.tutes the material conditions of experience in the case in question is only of use because it carries us beyond possibility to actuality, and appeal to it is only necessary because the object is not really conceived or, in other words, because the so-called conception is not really a conception.
[12] For instance, it might at least be _argued_ that we know s.p.a.ce to be actual without knowing it to be necessary.
[13] _Not_ "together with the apprehension _that_ the elements are connected". Cf. p. 311.
Kant really treats his "objectively real" conceptions as if they were "fict.i.tious", even though he speaks of them as complete. Consequently, his conceptions not being conceptions proper, he is necessarily led to hold that an appeal to experience is needed in order to establish the reality of a corresponding object. Yet, this being so, he should have asked himself whether, without an appeal to perception, we could even say that a corresponding object was possible. That he did not ask this question is partly due to the fact that he attributes the form and the matter of knowledge to different sources, viz. to the mind and to things in themselves. While the conceptions involved in the forms of perception, s.p.a.ce, and time, and also the categories are the manifestations of the mind"s own nature, sensations, which form the matter of knowledge, are due to the action of things in themselves on our sensibility, and of this activity we can say nothing. Hence, from the point of view of our mind--and since we do not know things in themselves, this is the only point of view we can take--the existence of sensations, and therefore of objects, which must be given in perception, is wholly contingent and only to be discovered through experience. On the other hand, since the forms of perception and conception necessarily determine in certain ways the nature of objects, _if_ there prove to be any objects, the conceptions involved may be thought to determine what objects are possible, even though the very existence of the objects is uncertain. Nevertheless, on his own principles, Kant should have allowed that, apart from perception, we could discover _a priori_ at least the reality, even if not the necessity, of the objects of these conceptions. For his general view is that the forms of perception and the categories are only actualized on the occasion of the stimulus afforded by the action of things in themselves on the sensibility. Hence the fact that the categories and forms of perception are actualized--a fact implied in the very existence of the _Critique_--involves the existence of objects corresponding to the categories and to the conceptions involved in the forms of perception. On Kant"s own principles, therefore, we could say _a priori_ that there must be objects corresponding to these conceptions, even though their nature in detail could only be filled in by experience.[14]
[14] Cf. Caird, i. 604-5.
NOTE ON THE REFUTATION OF IDEALISM
This well-known pa.s.sage[1] practically replaces a long section,[2]
contained only in the first edition, on the fourth paralogism of pure reason. Its aim is to vindicate against "idealism" the reality of objects in s.p.a.ce, and it is for this reason inserted after the discussion of the second postulate. The interest which it has excited is due to Kant"s use of language which at least seems to imply that bodies in s.p.a.ce are things in themselves, and therefore that here he really abandons his main thesis.
[1] B. 274-9, M. 167-9. Cf. B. x.x.xix (note), M. xl (note).
[2] A. 367-80, Mah. 241-53.
Idealism is the general name which Kant gives to any view which questions or denies the reality of the physical world; and, as has been pointed out before,[3] he repeatedly tries to defend himself against the charge of being an idealist in this general sense. This pa.s.sage is the expression of his final attempt. Kant begins by distinguishing two forms which idealism can take according as it regards the existence of objects in s.p.a.ce as false and _impossible_, or as doubtful and _indemonstrable_. His own view, which regards their existence as certain and demonstrable, and which he elsewhere[4]
calls transcendental idealism, const.i.tutes a third form. The first form is the dogmatic idealism of Berkeley. This view, Kant says, is unavoidable, if s.p.a.ce be regarded as a property of things in themselves, and the basis of it has been destroyed in the _Aesthetic_.
The second form is the problematic idealism of Descartes, according to which we are immediately aware only of our own existence, and belief in the existence of bodies in s.p.a.ce can be only an inference, and an uncertain inference, from the immediate apprehension of our own existence. This view, according to Kant, is the outcome of a philosophical att.i.tude of mind, in that it demands that a belief should be proved, and apparently--to judge from what Kant says of Berkeley--it does not commit Descartes to the view that bodies in s.p.a.ce, if their reality can be vindicated, are things in themselves.
[3] Cf. p. 76.
[4] A. 369, Mah. 243; cf. B. 44, M. 27.
The a.s.sertion that the _Aesthetic_ has destroyed the basis of Berkeley"s view, taken together with the drift of the _Refutation_ as a whole, and especially of Remark I, renders it clear that the _Refutation_ is directed against Descartes and not Berkeley. Kant regards himself as having already refuted Berkeley"s view, as he here states it, viz. that the existence of objects in s.p.a.ce is _impossible_, on the ground that it arose from the mistake of supposing that s.p.a.ce, if real at all, must be a property of things in themselves, whereas the _Aesthetic_ has as he thinks, shown that s.p.a.ce can be, and in point of fact is, a property of phenomena. He now wants to prove--compatibly with their character as phenomena--that the existence of bodies in s.p.a.ce is not even, as Descartes contends, _doubtful_. To prove this he seeks to show that Descartes is wrong in supposing that we have no immediate experience of these objects. His method is to argue that reflection shows that internal experience presupposes external experience, i. e. that unless we were directly aware of spatial objects, we could not be aware of the succession of our own states, and consequently that it is an inversion to hold that we must reach the knowledge of objects in s.p.a.ce, if at all, by an inference from the immediate apprehension of our own states.
An examination of the proof itself, however, forces us to allow that Kant, without realizing what he is doing, really abandons the view that objects in s.p.a.ce are phenomena, and uses an argument the very nature of which implies that these objects are things in themselves.
The proof runs thus:
_Theorem._ "The mere but empirically determined consciousness of my own existence proves the existence of objects in s.p.a.ce external to me."
"_Proof._ I am conscious of my own existence as determined in time. All time-determination presupposes something permanent in perception.[5] This permanent, however, cannot be an intuition[6]
in me. For all grounds of determination of my own existence, which can be found in me, are representations, and as such themselves need a permanent different from them, in relation to which their change and consequently my existence in the time in which they change can be determined.[7] The perception of this permanent, therefore, is possible only through a _thing_ external to me, and not through the mere _representation_ of a thing external to me. Consequently, the determination of my existence in time is possible only through the existence of actual things, which I perceive external to me. Now consciousness in time is necessarily connected with the consciousness of the possibility of this time-determination; hence it is necessarily connected also with the existence of things external to me, as the condition of time-determination, i. e. the consciousness of my own existence, is at the same time an immediate consciousness of the existence of other things external to me."[8]
[5] _Wahrnehmung._
[6] _Anschauung._
[7] The text has been corrected in accordance with Kant"s note in the preface to the second edition, B. x.x.xix, M. xl.
[8] B. 275-6, M. 167.
The nature of the argument is clear. "In order to be conscious, as I am, of a determinate succession of my states, I must perceive something permanent as that in relation to which alone I can perceive my states as having a definite order.[9] But this permanent cannot be a perception in me, for in that case it would only be a representation of mine, which, as such, could only be apprehended in relation to another permanent. Consequently, this permanent must be a thing external to me and not a representation of a thing external to me.
Consequently, the consciousness of my own existence, which is necessarily a consciousness of my successive states, involves the immediate consciousness of things external to me."
[9] Cf. Kant"s proof of the first a.n.a.logy.
Here there is no way of avoiding the conclusion that Kant is deceived by the ambiguity of the phrase "a thing external to me" into thinking that he has given a proof of the existence of bodies in s.p.a.ce which is compatible with the view that they are only phenomena, although in reality the proof presupposes that they are things in themselves. In the "proof", the phrase "a thing external to me" must have a double meaning. It must mean a thing external to my body, i. e. any body which is not my body; in other words, it must be a loose expression for a body in s.p.a.ce. For, though the "proof" makes us appeal to the spatial character of things external to me, the _Refutation_ as a whole, and especially Remark II, shows that it is of bodies in s.p.a.ce that he is thinking throughout. The phrase must also, and primarily, mean a thing external to, in the sense of independent of, my mind, i. e. a thing in itself. For the nerve of the argument consists in the contention that the permanent the perception of which is required for the consciousness of my successive states must be a _thing_ external to me in opposition to the representation of a thing external to me, and a thing external to me in opposition to a thing external to me can only be a thing in itself. On the other hand, in Kant"s conclusion, "a thing external to me" can only mean a body in s.p.a.ce, this being supposed to be a phenomenon; for his aim is to establish the reality of bodies in s.p.a.ce compatibly with his general view that they are only phenomena. The proof therefore requires that things external to me, in order that they may render possible the consciousness of my successive states, should have the very character which is withheld from them in the conclusion, viz. that of existing independently of me; in other words, if Kant establishes the existence of bodies in s.p.a.ce at all, he does so only at the cost of allowing that they are things in themselves.[10]
[10] The ambiguity of the phrase "external to me" is pointed out in the suppressed account of the fourth paralogism, where it is expressly declared that objects in s.p.a.ce are only representations. (A. 372-3, Mah. 247). Possibly the introduction of an argument which turns on the view that they are not representations may have had something to do with the suppression.
Nevertheless, the _Refutation_ may be considered to suggest the proper refutation of Descartes. It is possible to ignore Kant"s demand for a permanent as a condition of the apprehension of our successive states, and to confine attention to his remark that he has shown that external experience is really immediate, and that only by means of it is the consciousness of our existence as determined in time possible.[11] If we do so, we may consider the _Refutation_ as suggesting the view that Descartes" position is precisely an inversion of the truth; in other words, that our consciousness of the world, so far from being an uncertain inference from the consciousness of our successive states, is in reality a presupposition of the latter consciousness, in that this latter consciousness only arises through reflection upon the former, and that therefore Descartes" admission of the validity of self-consciousness implicitly involves the admission _a fortiori_ of the validity of our consciousness of the world.[12]
[11] B. 277, M. 167 fin.
[12] Cf. Caird, i. 632 and ff.
Oxford: Printed at the Clarendon Press by HORACE HART, M.A.