DEFINITION AND PROVINCE OF LOGIC. 11 



seemed to be so ; the reason perhaps is, that men's logical 

 notions have not yet acquired the degree of extension, or of 

 accuracy, requisite for the estimation of the evidence proper 

 to those particular departments of knowledge. 



7. Logic, then, is the science of the operations of the 

 understanding which are subservient to the estimation of 

 evidence: both the process itself of advancing from known 

 truths to unknown, and all other intellectual operations in so 

 far as auxiliary to this. It includes, therefore, the operation 

 of Naming ; for language is an instrument of thought, as well 

 as a means of communicating our thoughts. It includes, also, 

 Definition, and Classification. For, the use of these operations 

 (putting all other minds than one's own out of consideration) 

 is to serve not only for keeping our evidences and the conclu- 

 sions from them permanent and readily accessible in the 

 memory, but for so marshalling the facts which we may at 

 any time be engaged in investigating, as to enable us to 

 perceive more clearly what evidence there is, and to judge with 

 fewer chances of error whether it be sufficient. These, there- 

 fore, are operations specially instrumental to the estimation of 

 evidence, and, as such, are within the province of Logic. 

 There are other more elementary processes, concerned in all 

 thinking, such as Conception, Memory, and the like ; but of 

 these it is not necessary that Logic should take any peculiar 

 cognizance, since they have no special connexion with the 

 problem of Evidence, further than that, like all other problems 

 addressed to the understanding, it presupposes them. 



Our object, then, will be, to attempt a correct analysis of 

 the intellectual process called Keasoning or Inference, and of 

 such other mental operations as are intended to facilitate this : 

 as well as, on the foundation of this analysis, and pari passu 

 with it, to bring together or frame a set of rules or canons for 

 testing the sufficiency of any given evidence to prove any 

 given proposition. 



With respect to the first part of this undertaking, I do 

 not attempt to decompose the mental operations in question 

 into their ultimate elements. It is enough if the analysis as 



