INTRODUCTION. 



not in the things, and the properties of mind are therefore 

 all important. It is true that these laws are verified in the 

 observation of the exterior world ; and it would seem that 

 they might have been gathered and proved by general- 

 isation, had they not already been in our possession. But 

 on the other hand, it may well be urged that we cannot 

 prove these laws by any process of reasoning or observation, 

 because the laws themselves are presupposed, as Leibnitz 

 acutely remarked, in the very notion of a proof. They are 

 the prior conditions of all thought and all knowledge, and 

 even to question their truth is to allow them true. Hartley 

 ingeniously refined upon this argument, remarking that if 

 the fundamental laws of logic be not certain, there must 

 exist a logic of a second order whereby we may determine 

 the degree of uncertainty : if the second logic be not certain, 

 there must be a third ; and so on ad infinitum. Thus we 

 must suppose either that absolutely certain laws of thought 

 exist, or that there is no such thing as certainty whatever. 1 



Logicians, indeed, appear to me to have paid insufficient 

 attention to the fact that mistakes in reasoning are always 

 possible, and of not unfrequent occurrence. The Laws 

 of Thought are often called necessary laws, that is, laws 

 which cannot but be obeyed. Yet as a matter of fact, who 

 is there that does not often fail to obey them ? They are 

 the laws which the mind ought to obey rather than what 

 it always does obey. Our thoughts cannot be the criterion 

 of truth, for we often have to acknowledge mistakes in 

 arguments of moderate complexity, and we sometimes only 

 discover our mistakes by collision between our expectations 

 and the events of objective nature. 



Mr. Herbert Spencer holds that the laws of logic are 

 objective laws, 2 and lie regards the mind as being in 

 a state of constant education, each act of false reasoning 

 or miscalculution leading to results which are likely to 

 prevent similar mistakes from being again committed. 

 I am quite inclined to accept such ingenious views ; but 

 at the same time it is necessary to distinguish between the 

 accumulation of knowledge, and the constitution of the 

 mind which allows of the acquisition of knowledge. 

 Before the mind can pe-rceive or reason at all it must have 



1 Hartley on Man, vol. i. p. 359. 



' J Principles of Psychology, Second Ed., vol. ii. p. 86. 



