INTRODUCTION. 



mistakes in arguments of very moderate complexity, and 

 we sometimes only discover our mistakes by a collision 

 between our mental expectations and the events of ob- 

 jective nature. 



Mr. Herbert Spencer holds that the laws of logic are 

 objective laws f , and he regards the mind as being in 

 a state of constant education, each act of false reasoning 

 or miscalculation 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 experience, and the 

 constitution of the mind which allows of the acquisition 

 of knowledge. Before the mind can perceive or reason 

 at all it must have the conditions of thought impressed 

 upon it. Before a mistake can be committed, the mind 

 must clearly distinguish the mistaken conclusion from all 

 other assertions. Are not the Laws of Identity and 

 Difference the prior conditions of all consciousness and 

 all existence 1 Must they not hold true, alike of things 

 material and immaterial 1 and if so, can we say that 

 they are only subjectively true or objectively true ? I 

 am inclined, in short, to regard them as true both 'in 

 the nature of thought arid things/ as I expressed it in. 

 my first logical essays, and I hold that they belong to 

 the common basis of all existence. But this is one of 

 the most profound and difficult questions of psychology 

 and metaphysics which can be raised, and it is hardly 

 one for the logician to decide. As the mathematician does 

 not inquire into the nature of unity and plurality, but 

 developes the formal laws of plurality, so the logician, 

 as I conceive, must assume the truth of the Laws of 



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

 s * Pure Logic, or the Logic of Quality apart from Quantity,' London 

 (Stanford), 1864, pp. 10, 16, 22, 29, 36, &c. 



