INTRODUCTION. 



above definition with an amendment ; 

 he has defined Logic to be the 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 analysis, for conducting the pro- 

 cess correctly. There can be no 

 doubt as to the propriety of the emen- 

 dation. A right understanding of 

 the mental process itself, of the con- 

 ditions 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 pos- 

 sibly be founded. Art necessarily 

 presupposes knowledge ; art, in any 

 but its infant state, presupposes scien- 

 tific knowledge : and if every art 

 does not bear the name of a science, 

 it is only because several sciences are 

 often necessary to form the ground- 

 work of a single art. So complicated 

 are the conditions which govern our 

 practical agency, that to enable one 

 thing to be done, it is often requisite 

 to know the nature and properties of 

 many things. 



Logic, then, comprises the science of 

 reasoning, as well as an art, founded on 

 that science. But the word Reason- 

 ing, again, like most other scientific 

 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 sufficient 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 demonstra- 

 tions of geometry. 



Writers on logic have generally 

 preferred the former acceptation of 

 the term : the latter, and more exten- 

 sive 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 



sufficient reasons will, I believe, un- 

 fold 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 

 susceptible, does not seem to compre- 

 hend 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 sub- 

 ject only of the third part : the two 

 former treated of Terms, and of Pro- 

 positions ; under one or other of which 

 heads were also included Definition 

 and Division. By some, indeed, these 

 previous topics were professedly intro- 

 duced only on account of their con- 

 nexion 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 

 recent writers on logic have generally 

 understood the term as it was em- 

 ployed 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 pre- 

 cision of language, and accuracy of 

 classification : and we perhaps oftener 

 hear persons speak of a logical ar- 

 rangement, or of expressions logically 

 defined, than of conclusions logically 

 deduced from premises. Again, a 

 man is often called a great logician, 

 or a man of powerful logic, not for 



