INTRODUCTION. 



§ 1. 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 delivering 

 different ideas. Ethics and jurisprudence are liable to. the remark in com- 

 mon 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 favor. 



This diversity is not so much an evil to be complained of, as an inevita- 

 ble 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 any thing, 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. According- 

 ly, in the case of so complex an aggregation of particulars as are compre- 

 hended in any thing 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- 

 selves, we can not fix upon the most correct and compact mode of circum- 

 scribing them by a general description. It was not until after an extensive 

 and accurate acquaintance with the details of chemical phenomena, that it 

 was found possible to frame a rational definition of chemistry; and the 

 definition of the science of life and organization is still a matter of dispute. 

 So long as the sciences ai'e 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 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 subject of this volume. 



§ 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 above definition with an amendment ; he has de- 



* Archbishop Whately. ^ 



2 



