460 FALLACIES. 



do not reflect that the idea, being a result of abstraction, ought to 

 conform to the facts, and cannot make the facts conform to it. The 

 argument is at most admissible as an appeal to authority ; a surmise, 

 that what is now part of the idea must, before it became so, have been 

 found by previous inquirers in the facts. Nevertheless, the j^hiloso- 

 pher who more than all others has made profession of rejecting author- 

 ity, Descartes, constructed his philosophical system on this very basis. 

 His favorite device for arriving at truth, even in regai'd to outward 

 things, was by looking into his own mind for it. " Credidi me," says 

 his celebrated maxim, " pro regula generali sumere posse, omne id 

 quod valdi^ dilucide et distincte concipiebam, verum esse :" whatever 

 can be very clearly conceived, must certainly exist; that is, as he af- 

 terwards explains it, if the idea includes existence. And upon this 

 ground he infers that geometrical figures really exist, because they 

 can be distinctly conceived. Wlienever existence is " involved in an 

 idea," a thing conformable to the idea must really exist ; which is as 

 much as to say, whatever the idea contains must have its equivalent in 

 the thing ; and what we are not able to leave out of the idea cannot 

 be absent from the reality. This assumption pervades the philosophy 

 not, only of Descartes, but of all the thinkers who received their im- 

 pulse mainly from him, in particular the two most remarkable among 

 them, Leibnitz and Spinosa, from whom the modern Gennan meta- 

 physical philosophy is essentially an emanation. The esteemed author 

 of one of the Bridgewater Treatises (which for its accumulation of 

 scientific facts, and even for some of its generalizations, is worthy of 

 all praise) has fallen, as it seems to rne, into a similar fallacy when, 

 after arguing in rather a curious way to prove that matter may exist 

 without any of the known properties of matter, and may therefore be 

 changeable, he concludes that it cannot be eternal, because " etenial 

 (passive) existence necessarily involves incapability of change." I 

 beUeve it would be difficult to point out any other connexion betw^een 

 the facts of eternity and unchangeableness, than a strong association 

 between the two ideas. 



The other fonn of the fallacy ; Things' which we cannot think of 

 together cannot exist together — inchiding as one of its branches, that 

 what we cannot think of as existing, cannot exist at all — may be thus 

 briefly expressed : Whatever is inconceivable must be false. 



Against this prevalent doctrine I have sufficiently argued in a former 

 Book,* and nothing is required, in this place, but examples. It was 

 long held that Antipodes were impossible, because of the difficulty 

 which men found in conceiving persons with their heads in the same 

 direction as our feet. And it was one of the received arguments 

 against the Copernican system, that we cannot conceive so great a 

 void space as that system supposes to exist in the celestial regions. 

 When men's imaginations had always been used to conceive the stars 

 as firmly set in solid spheres, they naturally found much difficulty in 

 imagining them in so different, and, as it doubtless appeared to them, 

 so unsafe a situation. But men had no right to mistake the limitation 

 (whether natural, or, as it in fact proved, only artificial) of their own 

 faculties, for an inherent limitation of the possible modes of existence 

 in the universe. 



* Supra, pp, ] 56-161. 



