DEFINITION AND PROVINCE OF LOGIC. 9 



of their several callings. It is the only occupation in which 

 the mind never ceases to be engaged ; and is the subject, not 

 of logic, but of knowledge in general. 



Logic, however, is not the same thing with knowledge, 

 though the field of logic is coextensive with the field of know 

 ledge. Logic is the common judge and arbiter of all parti 

 cular investigations. It does not undertake to find evidence, 

 but to determine whether it has been found. Logic neither 

 observes, nor invents, nor discovers ; but judges. It is no part 

 of the business of logic to inform the surgeon what appearances 

 are found to accompany a violent death. This he must learn 

 from his own experience and observation, or from that of 

 others, his predecessors in his peculiar pursuit. But logic sits 

 in judgment on the sufficiency of that observation and expe 

 rience to justify his rules, and on the sufficiency of his rules 

 to justify his conduct. It does not give him proofs, but 

 teaches him what makes them proofs, and how he is to judge 

 of them. It does not teach that any particular fact proves any 

 other, but points out to what conditions all facts must con 

 form, in order that they may prove other facts. To decide 

 whether any given fact fulfils these conditions, or whether facts 

 can be found which fulfil them in a given case, belongs ex 

 clusively to the particular art or science, or to our knowledge 

 of the particular subject. 



It is in this sense that logic is, what Bacon so expressively 

 called it, ars artium ; the science of science itself. All science 

 consists of data and conclusions from those data, of proofs and 

 what they prove : now logic points out what relations must 

 subsist between data and whatever can be concluded from 

 them, between proof and everything which it can prove. If 

 there be any such indispensable relations, and if these can be 

 precisely determined, every particular branch of science, as 

 well as every individual in the guidance of his conduct, is 

 bound to conform to those relations, under the penalty of 

 making false inferences, of drawing conclusions which are not 

 grounded in the realities of things. Whatever has at any 

 time been concluded justly, whatever knowledge has been 

 acquired otherwise than by immediate intuition, depended on 



