266 REASONING. 



the negation of the truth is not only false, but impossible ; in 

 which we cannot, even by an effort of imagination, or in a sup- 

 position, conceive the reverse of that which is asserted. That 

 there are such truths cannot be doubted. We may take, for 

 example, all relations of number. Three and Two added to- 

 gether make Five. We cannot conceive it to be otherwise. 

 We cannot, by any freak of thought, imagine Three and Two 

 to make Seven."* 



Although Dr. Whewell has naturally and properly employed 

 a variety of phrases to bring his meaning more forcibly home, 

 he would, I presume, allow that they are all equivalent; and 

 that what he means by a necessary truth, would be sufficiently 

 defined, a proposition the negation of which is not only false 

 but inconceivable. I am unable to find in any of his expres- 

 sions, turn them what way you will, a meaning beyond this, 

 and I do not believe he would contend that they mean any- 

 thing more. 



This, therefore, is the principle asserted : that propositions, 

 the negation of which is inconceivable, or in other words, which 

 we cannot figure to ourselves as being false, must rest on evi- 

 dence of a higher and more cogent description than any which 

 experience can afford. 



Now I cannot but wonder that so much stress should be 

 laid on the circumstance of inconceivableness, when there is 

 such ample experience to show, that our capacity or incapacity 

 of conceiving a thing has very little to do with the possibility 

 of the thing in itself; but is in truth very much an affair 

 of accident, and depends on the past history and habits of our 

 own minds. There is no more generally acknowledged fact 

 in human nature, than the extreme difficulty at first felt in 

 conceiving anything as possible, which is in contradiction to 

 long established and familiar experience ; or even to old 

 familiar habits of thought And this difficulty is a necessary 

 result of the fundamental laws of the human mind. When 

 we have often seen and thought of two things together, and 

 have never in any one instance either seen or thought of them 



* History of Scientific Ideas, i. 58, 59. 



