ch. ix.] PHILOSOPHY AS AN ORGANON. 239 



the two variations. In point of fact there are such interfer- 

 ing conditions, due partly to the control exercised by the 

 sympathetic nerve over the contraction anc 1 dilatation of the 

 cerebral blood-vessels, and partly to other circumstances too 

 complicated to be here mentioned. 



Now it is the business of logic to codify, upon abstract 

 principles, the rules of scientific investigation ; to determine 

 what shall be admitted as trustworthy evidence, and what 

 shall not be so admitted ; to point out the class of problems 

 which each implement of research is best fitted to solve ; 

 and to enumerate the precautions which must be taken in 

 order to use each implement with skill and success. Logic 

 is therefore a science which contributes to all the others, and 

 to which all the others contribute. Though we may, and 

 indeed must, acquire familiarity with its methods by direct 

 practice in the study of the various sciences, yet the 

 advantage of understanding the general theory of those 

 methods, as a science by itself, cannot well be questioned 

 after the foregoing explanation. To become familiar with the 

 values of different kinds of evidence, and with the processes 

 by which evidence is procured, a lawyer must practise in 

 court ; yet every lawyer thinks it necessary to master the 

 general theory of evidence as presented in special treatises. 

 Logic is to the philosopher and the scientific inquirer what 

 the law of evidence is to the lawyer ; and the need for its 

 theoretical study rests upon the admitted principle that, in all 

 branches of human activity, rational knowledge is better than 

 empirical knowledge. In order to be always sure that we are 

 generalizing correctly, we must make the generalizing process 

 itself a subject of generalization. 



But although Comte did not dignify logic with the rank of 

 an independent science, he more than atoned for the omission 

 by his contributions to the study of logic. Since the era of 

 Bacon and Descartes, no book had appeared containing such 

 profound views of scientific method as the " Philosophie 



