11 



Here then we have a difficulty: the test of axioms is 

 that the contrary of them is inconceivable ; and yet persons, 

 till they have in some measure studied the subject, do not 

 see this inconceivableness. Hence our Axioms must be evi- 

 dent only to a small number of thinkers ; and seem not to 

 deserve the name of self-evident or necessary truths. 



This difficulty has been strongly urged by Mr Mill, as 

 supporting his view, that all knowledge of truth is derived 

 from experience. And in order that the opposite doctrine, 

 which I have advocated, may not labour under any disad- 

 vantages which really do not belong to it, I must explain, that 

 I do not by any means assert that those truths which I regard 

 as necessary, are all equally evident to common thinkers, 

 or evident to persons in all stages of intellectual develope- 

 ment. I may even say, that some of those truths which I 

 regard as necessary, and the necessity of which I believe the 

 human mind to be capable of seeing, by due preparation and 

 thought, are still such, that this amount of preparation and 

 thought is rare and peculiar ; and I will willingly grant, that 

 to attain to and preserve such a clearness and subtlety of 

 mind as this intuition requires, is a task of no ordinary 

 difficulty and labour. 



This doctrine, that some truths may be seen by intui- 

 tion, but yet that the intuition of them may be a rare and 

 difficult attainment, I have not, it would seem, conveyed 

 with sufficient clearness to obviate misapprehension. Mr Mill 

 has noticed a passage of my Philosophy on this subject, which 

 he has understood in a sense different from that which I 

 intended. Speaking of the two Principles of Chemical Science, 

 that combinations are definite in kind, and in quantity, 

 I had tried to elevate myself to the point of view in which 

 these Principles are seen, not only to be true, but to be 

 necessary. I was aware that even the profoundest chemists 

 had not ventured to do this ; yet it appeared to me that 



