12 INTRODUCTION. 



has at any time been concluded justly, whatever know- 

 ledge has been acquired otherwise than by immediate 

 intuition, depended upon the observance of the laws, 

 which it is the province of logic to investigate. If the 

 conclusions are just, and the knowledge sound, those 

 laws have actually been observed. 



6. We need not, therefore, seek any farther for 

 a solution of the question, so often agitated, respect- 

 ing the utility of logic. If a science of logic exists, or 

 is capable of existing, it must be useful. If there be 

 rules to which every mind conforms in every instance 

 in which it judges rightly, there seems little necessity 

 for discussing whether a person is more likely to 

 observe those rules, when he knows the rules, than 

 when he is unacquainted with them. 



A science may undoubtedly be brought to a certain, 

 not inconsiderable, stage of advancement, without the 

 application of any other logic to it than what all per- 

 sons, who are said to have a sound understanding, 

 acquire empirically in the course of their studies. 

 Men judged of evidence, and often very correctly, 

 before logic was a science, or they never could have 

 made it one. And they executed great mechanical 

 works before they understood the laws of mechanics. 

 But there are limits both to what mechanicians can 

 do without principles of mechanics, and to what 

 thinkers can do without principles of logic. And the 

 limits, in the two cases, are of the same kind. The 

 extent of what man can do without understanding the 

 theory of what he is doing, is in all cases much the 

 same : he can do whatever is very easy ; what requires 

 only time, and patient industry. But in the progress 

 of science from its easiest to its more difficult pro- 

 blems, every great step in advance has had either as 



