INTRODUCTION. 



correspond to the thoughts and things expressed, in order 

 that they shall serve their intended purpose. We may 

 therefore say that logic treats ultimately of thoughts and 

 things, and immediately of the signs which stand for them. 

 Signs, thoughts, and exterior objects may be regarded as 

 parallel and analogous series of phenomena, and to treat 

 any one of the three series is equivalent to treating either 

 of the other series. 



The Process of Inference. 



The fundamental action of our reasoning faculties 

 consists in inferring or carrying to a new instance of a 

 phenomenon whatever we have previously known of its 

 like, analogue, equivalent or equal. Sameness or identity 

 presents itself in all degrees, and is known under various 

 names ; but the great rule of inference embraces all 

 degrees, and affirms that so far as there exists sameness, 

 identity or likeness, what is true of one thing will be true 

 of tlie other. The great difficulty doubtless consists in 

 ascertaining that there does exist a sufficient degree of 

 likeness or sameness to warrant an intended inference ; 

 and it will be our main task to investigate the conditions 

 under which reasoning is valid. In this place I wish to 

 point out that there is something common to all acts 

 of inference, however different their apparent forms. The 

 one same rule lends itself to the most diverse applications. 



The simplest possible case of inference, perhaps, occurs 

 in the use of a pattern, example, or, as it is commonly 

 called, a sample. To prove the exact similarity of two 

 portions of commodity, we need not bring one portion 

 beside the other. It is sufficient that we take a sample 

 which exactly represents the texture, appearance, and 

 general nature of one portion, and according as this 

 sample agrees or not with the other, so will the two 

 portions of commodity agree or differ. Whatever is true 

 as regards the colour, texture, density, material of the 

 sample will be true of the goods themselves. In such 

 cases likeness of quality is the condition of inference. 



Exactly the same mode of reasoning holds true of 

 magnitude and figure. To compare the sizes of two 

 objects, we need not lay them beside each other. A 



