2 INTRODUCTION. 



that it was found possible to frame a rational definition of 

 chemistry ; and the definition of the science of life and orga- 

 nization is still a matter of dispute. So long as the sciences 

 are imperfect, the definitions must partake of their imperfec- 

 tion ; and if the former are progressive, the latter ought to be 

 so too. As much, therefore, as is to be expected from a defi- 

 nition placed at the commencement of a subject, is that it 

 should define the scope of our inquiries : and the definition 

 which I am about to offer of the science of logic, pretends to 

 nothing more, than to be a statement of the question which I 

 have put to myself, and which this book is an attempt to 

 resolve. The reader is at liberty to object to it as a definition 

 of logic ; but it is at all events a correct definition of the sub- 

 ject of these volumes. 



2. Logic has often been called the Art of Beasoning. 

 A writer* who has done more than any other person to restore 

 this study to the rank from which it had fallen in the esti- 

 mation of the cultivated class in our own country, has adopted 

 the 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 process cor- 

 rectly. 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 every art does 

 not bear the name of a science, it is only because several 

 sciences are often necessary to form the groundwork of a single 

 art. So complicated are the conditions which govern our prac- 

 tical agency, that to enable one thing to be done, it is often 

 requisite to know the nature and properties of many things. 



* Archbishop Whately. 



