316 REASONING. 



space or time, or two straight lines inclosing a space, 

 Newton himself had not been able to realize the con- 

 ception, or we should not have had his hypothesis of 

 a subtle ether, the occult cause of gravitation ; and 

 his writings prove, that although he deemed the par- 

 ticular nature of the intermediate agency a matter 

 of conjecture, the necessity of some such agency 

 appeared to him indubitable. It would seem that 

 even now the majority of scientific men have not 

 completely got over this very difficulty ; for though 

 they have at last learnt to conceive the sun attracting 

 the earth without any intervening fluid, they cannot 

 yet conceive the sun illuminating the earth without 

 some such medium. 



If, then, it be so natural to the human mind, even 

 in its highest state of culture, to be incapable of con- 

 ceiving, and on that ground to believe impossible, 

 what is afterwards not only found to be conceivable 

 but proved to be true ; what wonder 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 variance with the association, the ac- 

 quired incapacity should continue, 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 although 

 we never saw them fall, nor -ever perhaps imagined 

 them falling, we have seen so many other things fall, 

 that we have innumerable 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 conceive a slight 



