58 HUME I 



do I know ? They furnish us with the results of 

 the mental operations which constitute thinking; 

 while philosophy, in the stricter sense of the term, 

 inquires into the foundation of the first principles 

 which those operations assume or imply. 



But though, by reason of the special purpose of 

 philosophy, its distinctness from other branches of 

 scientific investigation may be properly vindicated, 

 it is easy to see that, from the nature of its subject- 

 matter, it is intimately and, indeed, inseparably 

 connected with one branch of science. For it is 

 obviously impossible to answer the question, What 

 can we know ? unless, in the first place, there is a 

 clear understanding as to what is meant by know- 

 ledge ; and, having settled this point, the next 

 step is to inquire how we come by that which we 

 allow to be knowledge ; for, upon the reply, 

 turns the answer to the further question, whether, 

 from the nature of the case, there are limits to 

 the knowable or not. While, finally, inasmuch as 

 What can I know ? not only refers to knowledge 

 of the past or of the present, but to the confident 

 expectation which we call knowledge of the 

 future ; it is necessary to ask, further, what 

 justification can be alleged for trusting to the 

 guidance of our expectations in practical conduct. 



It surely needs no argumentation to show, that 

 the first problem cannot be approached without 

 the examination of the contents of the mind ; and 

 the determination of how much of these contents 



