318 REASONING. 



which in this case reduces itself to simple inspection, 

 we cannot so much as call up in our imagination two 

 straight lines, in order to attempt to conceive them 

 inclosing a space, without by that very act repeating 

 the philosophical experiment which establishes the 

 contrary. Will it really be contended that the incon- 

 ceivableness of the thing, under such circumstances, 

 proves anything against the experimental origin of the 

 conviction ? Is it not clear that in whichever mode 

 our belief in the proposition may have originated, the 

 impossibility of our conceiving the negative of it must, 

 under either hypothesis, be the same? As, then, 

 Mr. Whewell exhorts those who have any difficulty 

 in recognising the distinction held by him between 

 necessary and contingent truths, to study geometry, 

 a condition which I can assure him I have con- 

 scientiously fulfilled, I, in return, with equal confi- 

 dence, exhort those who agree with Mr. Whewell, to 

 study the elementary laws of association ; being con- 

 vinced that nothing more is requisite than a moderate 

 familiarity with those laws, to dispel the illusion 

 which ascribes a peculiar necessity to our earliest 

 inductions from experience, and measures the possi- 

 bility of things in themselves, by the human capacity 

 of conceiving them. 



I hope to be pardoned for adding, that Mr. Whe- 

 well himself has both confirmed by his testimony the 

 effect of habitual association in giving to an expe- 

 rimental truth the appearance of a necessary one, and 

 afforded a striking instance of that remarkable law 

 in his own person. In his Philosophy of the Inductive 

 Sciences he continually asserts, that propositions 

 which not only are not self-evident, but which we 

 know to have been discovered gradually, and by great 



