The Philosophical Review/Volume 1/Review: Twardowski - Idee und Perception
This little pamphlet will be read with a great deal of interest by students of Descartes. Either a very important point of the Cartesian doctrine has been overlooked, or the author may be accused of reading his own thoughts into a system which he intends to interpret. At any rate, the testimony adduced justifies a rehearing of the case.
The criterion of truth is, according to Descartes, the clara et distincta perceptio. Perception is neither an act of ideation nor the idea itself, but the subjective act of apprehension (Wahrnehmung). A perception is clear which is present and manifest to an attentive mind, it is distinct in so far as it is marked off from all other perceptions. These conditions are fulfilled only by the perceptio ab intellectu or, as we should say, inner perception. Such a clear and distinct perception is an evident one, the cause of a true judgment. Now, the terms clearness and distinctness, when defining the idea, are not employed in the same sense as in the former case. An idea is distinct when it is accurately marked off from other ideas, clear when it contains its essential property. Descartes' use of the phrase "clear and distinct idea" is synonymous with what modern logic calls notion (Begriff). The clear and distinct perception is the cause of the validity of a judgment, whereas the clearness and distinctness of an idea are only conditions of the judgment's correctness.
On the whole, it seems to me, we must accept the interpretation offered by M. Twardowski. The fact that Descartes sometimes uses the terms intelligere and concipere interchangeably with percipere will no doubt be instanced as an objection against confining the principle of truth to the inner perception. Still, the latter verb occurs more frequently than the others, and in the meaning given to it by the author appears to express the philosopher's thought most clearly. No knowledge, Descartes holds, is more certain than the existence of a thinking subject, and this is based on such an immediate perception or intuition. On this truth as the fundamental proposition the whole chain of reasoning is based; every succeeding deduction must stand the test of the criterion, if it is to have any validity whatever. I also mention the Cartesian argument for the existence of God as bearing out M. Twardowski's statement. If the clearness and distinctness of the idea formed the criterion, the mere presence in the mind of such an idea of God would be sufficient evidence of his reality. But Descartes' proof is not merely ontological, it is anthropological. There is present in the soul an idea of God, which possesses more reality than all other ideas. It is clearly manifest that everything must have its cause, and that the efficient cause must have at least as much reality as the effect. Therefore God exists (Med. III, Pr. ph., I, 17). In the entire chain of reasoning no proposition is accepted as true unless it meets the requirements of the regula generalis.
M. Twardowski's book is as valuable as it is short. In calling attention to a distinction which has been almost universally ignored, he brings us much nearer to a clear understanding of Cartesian epistemology than we were before.
Frank Thilly.
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