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450 The second chapter of the introduction traces the subsequent fortunes of Reid's philosophy in Britain, France, and America. Special prominence is here again given to Hamilton, whom the editor styles "the ablest exponent and special defender of the Scottish realism," an "appreciation" which, after Mill's Examination and Dr. Stirling's Hamilton and the Philosophy of Perception, is a little unguarded. No mention is made of the important and interesting development of Reid's principle by Professor Campbell Fraser, in his insistence upon the ultimate philosophical necessity of a faith which, if unreasoned or only in part reasoned out to logical coherence, is, none the less, of the essence of reason.

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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