230 HABIT AND INTELLIGENCE. [chap. 



that logic 1. The fallacy that logic is an organon of discovery, 

 orsauou of "^^^^^ ^^^ ^^^ eiTor of the scholastic philosophy, and was 

 discovery: that against which Bacon's whole philosophical career was 

 employed in contending. It is now so completely dis- 

 credited that I need not spend many words in refuting it. 

 I have stated in a former chapter^ what is now the ■univer- 

 sally received conclusion on this subject ; — namely, that 

 the function of logic, regarded as a science, is not to extend 

 the structure of our knowledge, but to fix its foundations, 

 that 2. The fallacy that mathematics is the type of all 



matictis science. Mathematics is altogether a deductive science; 

 the type that is to Say, it is a science of pure reasoning ; and con- 



of SCIGIICC ' " 



' sequently it cannot possibly be the type of sciences of 



observation like anatomy and histology, or sciences of 



experiment like chemistry. Even if chemistry hereafter 



becomes in part a mathematical science, as the sciences 



of electricity and heat have done, yet, like them, it must 



always continue to be in part experimental, and in so far 



as it is experimental, it cannot be mathematical. 



that 3. The fallacy that simplicity and intelligibleness are 



aud intel- tests of truth. This was formularized as an axiom by 



hgibleness Descartes, who laid down as the foundation of his philo- 



are tests of . ^ 



truth: sophy that what is conceivable with perfect clearness 

 must be true. This was the error of a geometrician ; for, 

 in geometry, nothing can be clearly conceived unless it is 

 true ; and whatever is true must necessarily be clearly 

 conceived as soon as it is fully understood. In physical 

 science, -on the contrary, truth is mere truth of fact, and 

 error consequently involves no logical absurdity ; and a 

 conception may be clear and yet not true. But though it 

 is not true that clearness is a test of truth, yet it is true 

 that inability to attain to clearness is a proof of imperfect 

 knowledge. Yet even this test must be applied with 

 caution ; for there are many subjects on which our know- 

 ledge must always be imperfect ; — I do not mean merely 

 limited in extent, but surrounded with a kind of haze of 

 mystery : this is especially true of the mutual relation of 

 the conscious and the unconscious life, and of all the facts 



^ The chapter on the Classification of the Sciences (Chap. XLIIL). 



