INTRODUCTION 



§ I. There is as great diversity 

 among authors in the modes which 

 they have adopted of defining logic, as 

 in their treatment of the details of 

 it. This is what might naturally be 

 expected on any subject on which 

 writers have availed themselves of 

 the same language as a means of de- 

 livering different ideas. Ethics and 

 jurisprudence are liable to the remark 

 in common with logic. Almost every 

 writer having taken a different view 

 of some of the particulars which these 

 branches of knowledge are usually 

 understood to include, each has so 

 framed his definition as to indicate 

 beforehand his own peculiar tenets, 

 and sometimes to beg the question in 

 their favour. 



This diversity is not so much an 

 evil to be complained of, as an inevit- 

 able and in some degree a proper 

 result of the imperfect state of those 

 sciences. It is not to be expected 

 that there should be agreement about 

 the definition of anything, until there 

 is agreement about the thing itself. 

 To define, is to select from among all 

 the properties of a thing, those which 

 shall be understood to be designated 

 and declared by its name ; and the 

 properties must be well known to us 

 before we can be competent to deter- 

 mine which of them are fittest to be 

 chosen for this purpose. Accordingly, 

 in the case of so complex an aggrega- 

 tion of particulars as are compre- 

 hended in anything which can be 

 called a science, the definition we set 

 out with is seldom that which a more 

 extensive knowledge of the subject 



' shows to be the most appropriate. 

 Until we know the particulars them- 



I selves, we cannot fix upon the most 

 correct and compact mode of circum- 

 scribing them by a general descrip- 

 tion. It was not until after an ex- 

 tensive and accurate acquaintance 

 with the details of chemical pheno- 

 mena, that it was found possible to 

 frame a rational definition of chemis- 

 try ; and the definition of the science 

 of life and organization is still a 

 matter of dispute. So long as the 

 sciences are imperfect, the definitions 

 must partake of their imperfection ; 

 and if the former are progressive, the 

 latter ought to be so too. As much, 

 therefore, as is to be expected from a 

 definition placed at the commence- 

 ment 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 state- 

 ment 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 defini- 

 tion of logic ; but it is at all events 

 a correct definition of the subject of 

 these volumes. 



§ 2. Logic has often been called 

 the Art of Reasoning. A writer* 

 who has done more than any other 

 person to restore this study to the 

 rank from which it had fallen in the 

 estimation of the cultivated class in 

 our own country, has adopted the 



* Archbishop Whately. 

 A 



