56 DOGMATISM AND EVOLUTION 



things' are themselves directly perceived; and the 'images' can 

 be compared with the 'real things' and thus corrected by them. 

 The representative theory in all its forms contains the following 

 difficulty. On the one hand, there is nothing in the idea by 

 which its correspondence with the thing, or even the existence of 

 the thing, can be attested; and yet, on the other hand, it is only 

 through the idea that the existence and nature of the thing can 

 be known. The difficulty is evaded somewhat as follows. It is 

 not anything in the idea (i. e., it is no part of its logical content, 

 or of its psychological structure) that indicates its correctness, 

 but some character that can vary independently of the content 

 or structure. Thus the empiricist observes that sensations (as 

 over against the precisely similar ideas of imagination) are dis- 

 tinguished by a peculiar intensity, steadiness, vividness, or emo- 

 tional setting, or by their direct dependence upon the sense- 

 organs; and any or all of these may be regarded as assuring the 

 correctness of this class of ideas. On the other hand, the rational- 

 ist, rejecting the evidence of the senses, may specify the analytical 

 distinctness of the true ideas as the distinguishing mark. If a 

 ground be sought for any such theory, the empiricist who main- 

 tains it can only appeal to the observed fact, that such ideas as 

 he has named cannot be doubted. The inability to doubt may 

 be ascribed to two causes : the fixity of the idea itself in conscious- 

 ness, or the strength of the feeling of conviction which accom- 

 panies it. That a similar procedure is possible to rationalism 

 the example of Descartes shows. With him too the inability 

 to doubt is the ultimate proof of a true idea. His famous cri- 

 terion of truth is found inductively by the method of difference, 

 in fact. Having discovered an indubitable truth, he observes in 

 what respect this differs from all the ideas which he has previously 

 rejected as open to question; and this difference is then the 

 criterion. Descartes, however, adopts this position only as the 

 point of departure from which to reach a higher one. Ultimately, 

 as he believes, the ground of the criterion is to be found in the 

 veracity of God. The existence of a perfect being is thus a self- 



