DEMONSTRATION, AND NECESSARY TRUTHS. 269 



if in cases where the association is still older, more confirmed, 

 and more familiar, and in which nothing ever occurs to shake 

 our conviction, or even suggest to us any conception at vari- 

 ance with the association, the acquired incapacity should con- 

 tinue, and be mistaken for a natural incapacity? It is true, 

 our experience of the varieties in nature enables us, within 

 certain limits, to conceive other varieties analogous to them. 

 We can conceive the sun or moon falling; for though we 

 never saw them fall, nor ever perhaps imagined them falling, 

 we have seen so many other things fall, that we have innu- 

 merable familiar analogies to assist the conception ; which, 

 after all, we should probably have some difficulty in framing, 

 were we not well accustomed to see the sun and moon move 

 (or appear to move,) so that we are only called upon to con- 

 ceive a slight change in the direction of motion, a circum- 

 stance familiar to our experience. But when experience affords 

 no model on which to shape the new conception, how is it 

 possible for us to form it ? How, for example, can we imagine 

 an end to space or time? We never saw any object without 

 something beyond it, nor experienced any feeling without 

 something following it. When, therefore, we attempt to con- 

 ceive the last point of space, we have the idea irresistibly 

 raised of other points beyond it. When we try to imagine 

 the last instant of time, we cannot help conceiving another 

 instant after it. Nor is there any necessity to assume, as is 

 done by a modern school of metaphysicians, a peculiar funda- 

 mental law of the mind to account for the feeling of infinity 

 inherent in our conceptions of space and time ; that apparent 

 infinity is sufficiently accounted for by simpler and universally 

 acknowledged laws. 



Now, in the case of a geometrical axiom, such, for example, 

 as that two straight lines cannot inclose a space, a truth 

 which is testified to us by our very earliest impressions of the 

 external world, how is it possible (whether those external 

 impressions be or be not the ground of our belief) that the 

 reverse of the proposition could be otherwise than inconceiv- 

 able to us ? What analogy have we, what similar order of 

 facts in any other branch of our experience, to facilitate to us 



