Immanuel Kant's Critique of Pure Reason — trans. F. Max Müller

but outside each other, in order to be able to say, that the reciprocal sequence of the perceptions is founded in the object, and thus to represent their coexistence as objective. The relation of substances, however, of which the first has determinations the ground of which is contained in the other, is the relation of influence, and if, conversely also, the first contains the ground of determinations in the latter, the relation is that of community or reciprocity. Hence the coexistence of substances in space cannot be known in experience otherwise but under the supposition of reciprocal action : and this is therefore the condition also of the possibiHty of things themselves as objects of experience.

SUPPLEMENT XXI

[See vol. ii. p. 197]

An important protest, however, against these rules for proving existence mediately is brought forward by Idealism^ and this is therefore the proper place for its refutation.

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Refutation of Idealism

Idealism (I mean material idealism) is the theory which declares the existence of objects in space, without us, as either doubtful only and not demonstrable, or as false and impossible. The for77ier is the problematical idealism of Descartes, who declares one empirical assertion only to be undoubted, namely, that of / am ; the latter is the dogmatical ideaHsm of Berkeley, who declares space and all things to which it belongs as an inseparable condition, as something impossible in itself, and, therefore, the things in space as mere imaginations. Dogmatic idealism is inevitable, if we look upon space as a property belonging to things by themselves, for in that case space and all of which it is a condition, would be a non- entity. The ground on which that idealism rests has been removed by us in the transcendental ^sthe4;ic. Problematical idealism, which asserts nothing, but only pleads our inability of proving any existence except our own by means of immediate experience, is reasonable and in accordance with a sound philosophical mode of thought, which allows of no decisive judgment, before a sufficient proof has been found. The required proof will have to demonstrate that we may have not only an imagination, but also an experience of external things, and this it seems can hardly be effected in any other way except by proving that even our internal experience, which Descartes considers as

p. 778

Stipplement XXI 779

undoubted, is possible only under the supposition of external experience.

Theorem

The simple, but empirically determined Consciousness of my own existejice, proves the Existence of objects in space outside myself.

Proof

I am conscious of my own existence as determined in time, and all determination in time presupposes something permanent in the perception.^ That permanent, however, cannot be an intuition within me, because all the causes which determine my existence, so far as they can be found within me, are representations, and as such require themselves something permanent, different from them, in reference to which their change, and therefore my existence in time in which they change, may be determined. The perception of this permanent, therefore, is possible only through a thing outside me, and not through the mere representation of a thing outside me, and the determination of my existence in time is, consequently, possible only by the existence of real things, which I perceive outside me. Now, as the consciousness in time is necessarily connected with the consciousness of the possibility of that determination of time, it is also necessarily connected with the existence of things outside me, as the condition of the determination of time. In other words, the consciousness of my own existence is, at the same time, an immediate consciousness of the existence of other things.

Note i . — It will have been perceived that in the foregoing proof the trick played by idealism has been turned against it, and with greater justice. Idealism assumed that the only immediate experience is the internal, and that from it we can no more than i?tfer external things, though in an untrustworthy manner only, as always happens if from given effects we infer definite

^ This passage has been translated as amended by Kant himself in the Preface to the Second Edition (p. 386).

/So Supplement XXI