158 REASONING. 



ether; the occult cause of gravitation ; and his writings prove, that 

 although he deemed the particular nature of the inteiTnediate agency 

 a matter of conjecture, the necessity of some such agency appeared to 

 him indubitable. It would seem that even now the majority of scien- 

 tific men have not completely got over this very difficulty ; for though 

 they have at last learnt to conceive the sun attracting the eaith with- 

 out 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 conceiving, 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 confiraied, and more familiar, and in which nothing 

 ever occurs to shake our conviction, or even suggest to us any concep- 

 tion at variance with the association, the acquired incapacity should 

 continue, and be mistaken for a natural incapacity 1 It is true our ex- 

 perience 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 

 ima<Tined them falUng, 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 fi-aming, 

 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 

 change in the direction of motion, a circumstance familiar to our ex- 

 perience. But when experience affijrds 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 timel We neyer saw 

 any object without something beyond it, nor experienced- any feeling 

 without something following it. When, therefore, we attempt to 

 conceive the last point of space, we have the idea in-esistibly 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 the school to which Mr. 

 Whewell belongs, a peculiar fundamental 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 sim23ler 

 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 w^ich is testified to 

 us by our veiy earliest impressions of the external world — how is it 

 possible (whether those external impressions be or be not the gi-ound 

 of our belief) that the reverse of the proposition can be otherwise 

 than inconceivable' to us ? What analogy have we, what similar order 

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

 conception of two straight lines inclosing a space? Nor is even this 

 all. I have already called attention to the peculiar property of our 

 impressions of form, that the ideas or mental images exactly resemble 

 their prototypes, and adequately represent them for the purposes of 

 scientific observation. From this^ and fi-om the intuitive character of 

 the obsei-\^ation, which in this case reduces itself to simple inspection, 

 we cannot so m.uch as call up in our imagination two straight lines, in 

 order to attempt to conceive them inclosing a space, without by that 



