18 PART I. THE PROBLEM. 



accomplish if applied by even one adept. Had he divined the 

 interdependent unity of nature, as the latest science is increas- 

 ingly forcing it on our attention, he would have certainly 

 admitted that the most admirable of methods should allow for 

 progressive stages of certainty as regards conclusions, and for 

 an organic and historic development of the structure of know- 

 ledge from the simple to the complex. He would have there- 

 fore emphatically repudiated the idea of remaining reconciled 

 for a time to probable or incomplete results e.g., to X-rays, 

 cathode-rays, and Lenard-rays, 1 whose precise nature is as yet 

 a mystery, or to accessory food factors such as fat-soluble A, 

 water-soluble #, and the anti-scorbutic factor, where the func- 

 tions are only partially known and the chemical nature not at all. 

 It was this same laudable craving for certainty which obscured 

 for Descartes the practical value of the inductive method, and 

 which prevailed on him to exert his genius to the fullest 

 measure in order to elaborate a system of knowledge which 

 should remorselessly exclude all uncertainty. On this account, 

 he made in his Regulae a highly ingenious attempt by accen- 

 tuating intuitional truth, and coupling this with a stern deduc- 

 tive procedure where every movement is rigorously checked 

 to comprehend the Universe without an appeal to general 

 experience. Descartes was even jealous of the reasoning pro- 

 cess, and hence he proposed to fuse, through repeated attempts, 

 the links of a reasoning process, till it became one and 

 intuitional in character.- From the point of view of the 

 end aimed at, Descartes' attitude was irreproachable; only he 

 was unfortunately mistaken in his assumption that either the 

 reasoning process or the external world was composed of 

 discrete elements void of intricate and subtle interrelations. He 

 rightly distrusted reliance on the senses because of the evident 

 heterogeneity of what is presented to observation ; but he failed 

 to appreciate that words, being but symbols, are even more 

 elusive than facts, and that the most trifling slip in a com- 

 plicated train of reasoning may throw us altogether off the 

 track, whilst no amount of foresight can prevent such slips 

 from occurring where facts are not appealed to unceasingly. 1 ^ 



1 The X-rays are now practically identified with the gamma-rays of the 

 radio-active substances, and much is known concerning them, and the 

 cathode-rays are now said to consist of streams of negatively charged particles 

 or electrons. 



2 On the above, see the Regulae; also Boyce Gibson on these in Mind. 



3 Leibniz drew up rules referring to probable knowledge. His second 

 rule in his L'art de bien raisonner reads: "When it does not seem possible 

 to attain to certainty, one must content oneself with probability." (Couturat, 

 La logique de Leibnitz.) The following formal rules of his specially refer 

 to this type of knowledge: "(1) Distinguish degrees of probability. (2) A 

 conclusion is never more probable than the principle from which it is 

 deduced. (3) When a conclusion is deduced from several principles which 

 are only probable, the conclusion is less probable than any of those prin- 

 ciples." (Ibid., p. 180.) 



