ILLUSTRATIONS OF THE LOGIC OF SCIENCE. 287 



reader with what they have to say, if it were not such a striking ex- 

 ample of how they have been slumbering through ages of intellect- 

 ual activity, listlessly disregarding the enginery of modern thought, 

 and never dreaming of applying its lessons to the improvement of 

 logic. It is easy to show that the doctrine that familiar use and 

 abstract distinctness make the perfection of apprehension has its only 

 true place in philosophies which have long been extinct; and it is now 

 time to formulate the method of attaining to a more perfect clearness 

 of thought, such as we see and admire in the thinkers of our own 

 time. 



When Descartes set about the reconstruction of philosophy, his 

 first step was to (theoretically) permit skepticism and to discard the 

 practice of the schoolmen of looking to authority as the ultimate 

 source of truth. That done, he sought a more natural fountain of 

 true principles, and professed to find it in the human mind ; thus 

 passing, in the directest way, from the method of authority to that of 

 apriority, as described in my first paper, Self-consciousness was to 

 furnish us with our fundamental truths, and to decide what was 

 agreeable to reason. But since, evidently, not all ideas are true, he 

 was led to note, as the first condition of infallibility, that they must be 

 clear. The distinction between an idea see ming clear and really being 

 so, never occurred to him. Trusting to introspection, as he did, even for 

 a knowledge of external things, why should he question its testimony 

 in respect to the contents of our own minds? But then, I suppose, 

 seeing men, who seemed to be quite clear and positive, holding oppo- 

 site opinions upon fundamental principles, he was further led to say 

 that clearness of ideas is not sufficient, but that they need also to be 

 distinct, i. e., to have nothing unclear about them. What he probably 

 meant by this (for he did not explain himself with j^recision) was, that 

 they must sustain the test of dialectical examination ; that they must 

 not only seem clear at the outset, but that discussion must never be 

 able to bring to light points of obscurity connected with them. 



Such was the distinction of Descartes, and one sees that it was 

 precisely on the level of his philosophy. It was somewhat developed 

 by Leibnitz. This great and singular genius was as remarkable for 

 what he failed to see as for what he saw r . That a piece of mechanism 

 could not do work perpetually without being fed w T ith power in some 

 form, was a thing perfectly apparent to him ; yet he did not under- 

 stand that the machinery of the mind can only transform knowledge, 

 but never originate it, unless it be fed with facts of observation. He 

 thus missed the most essential point of the Cartesian philosophy, 

 which is, that to accept propositions which seem perfectly evident to 

 us is a thing which, whether it be logical or illogical, we cannot help 

 doing. Instead of regarding the matter in this way, he sought to re- 

 duce the first principles of science to formulas which cannot be denied 

 without self-contradiction, and was apparently unaware of the great 



