18 INTRODUCTION. 



fined Logic to be tlie Science, as well as the Art, of reasoning; meaning 

 by the former term, the analysis of the mental process which takes place 

 whenever we reason, and by the latter, the rules, grounded on that analy- 

 sis, for conducting the process correctly. There can be no doubt as to the 

 propriety of the emendation. A right understanding of the mental process 

 itself, of the conditions it depends on, and the steps of which it consists, 

 is the only basis on which a system of rules, fitted for the direction of the 

 process, can possibly be founded. Art necessarily presupposes knowledge ; 

 art, in any but its infant state, presupposes scientific knowledge : and if ev- 

 ery art does not bear the name of a science, it is only because several sci- 

 ences are often necessary to form the groundwork of a single art. So com- 

 plicated are the conditions which govern our practical agency, that to ena- 

 ble one thing to be done, it is often requisite to ktioio the nature and prop- 

 erties of many things. 



Logic, then, comprises the science of reasoning, as well as an art, found- 

 ed on that science. But the word Reasoning, again, like most other scien- 

 tific terms in popular use, abounds in ambiguities. In one of its accepta- 

 tions, it means syllogizing ; or the mode of inference which may be called 

 (with suflicient accuracy for the present purpose) concluding from generals 

 to particulars. In another of its senses, to reason is simply to infer any 

 assertion, from assertions already admitted : and in this sense induction is 

 as much entitled to be called reasoning as the demonstrations of geometry. 



Writers on logic have generally preferred the former acceptation of the 

 term : the latter, and more extensive signification is that in which I mean 

 to use it. I do this by virtue of the right I claim for every author, to give 

 whatever provisional definition he pleases of his own subject. But suffi- 

 cient reasons will, I believe, unfold themselves as we advance, why this 

 should be not only the provisional but the final definition. It involves, at 

 all events, no arbitrary change in the meaning of the word ; for, with the 

 general usage of the English language, the wider signification, I believe, 

 accords better than the more restricted one. 



§ 3. But reasoning, even in the widest sense of which the word is sus- 

 ceptible, does not seem to comprehend all that is included, either in the 

 best, or even in the most current, conception of the scope and province of 

 our science. The employment of the word Logic to denote the theory of 

 Argumentation, is derived from the Aristotelian, or, as they are commonly 

 termed, the scholastic, logicians. Yet even with them, in their systematic 

 treatises. Argumentation was the subject only of the third part: the two 

 former treated of Terms, and of Propositions ; under one or other of which 

 heads were also included Definition and Division. By some, indeed, these 

 previous topics were professedly introduced only on account of their con- 

 nection with reasoning, and as a preparation for the doctrine and rules of 

 the syllogism. Yet they were treated with greater minuteness, and dwelt 

 on at greater length, than was required for that purpose alone. More re- 

 cent writers on logic have generally understood the term as it was employ- 

 ed by the able author of the Port Royal Logic ; viz., as equivalent to the 

 Art of Thinking. Nor is this acceptation confined to books, and scientific 

 inquiries. Even in ordinary conversation, the ideas connected with the 

 word Logic include at least precision of language, and accuracy of classifi- 

 cation : and we perhaps oftener hear persons speak of a logical arrange- 

 ment, or of expressions logically defined, than of conclusions logically de- 

 duced from premises. Again, a man is often called a great logician, or a 



