FALLACIES OF SIMPLE INSPECTIOX. 



493 



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 liad 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 ap- 

 peared to them, so precarious a situa- 

 tion. But they had no right to mis- 

 take 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. 



It may be said in objection, that 

 the error in these cases was in the 

 minor premise, not the major ; an 

 error of fact, not of principle ; that it 

 did not consist in supposing that what 

 is inconceivable cannot be true, but in 

 supposing antipodes to be inconceiv- 

 able, when present experience proves 

 that they can be conceived. Even 

 if this objection were allowed, and the 

 proposition that what is inconceivable 

 cannot be true were suffered to remain 

 luiquestioned as a speculative truth, it 

 would be a truth on which no practi- 

 cal consequence could ever be founded, 

 since, on this showing, it is impossible 

 to affirm of any proposition, not being 

 a contradiction in terms, that it is in- 

 conceivable. Antipodes were really, 

 not fictitiously, inconceivable to our 

 ancestors : they are indeed conceiv- 

 able to us ; and as the limits of our 

 power of conception have been so 

 largely extended by the extension of 

 our experience and the more varied 

 exercise of our imagination, so may 

 posterity find many combinations per- 

 fectly conceivable to them which are 

 inconceivable to us. But, as beings 

 of limited experience, we must always 

 and necessarily have limited concep- 

 tive powers ; while it does not by any 

 means follow that the same limitation 

 obtains in the possibilities of nature, 

 nor even in her actual manifesta- 

 tions. 



Bather more than a century and a 



half ago it was a scientific maxim, 

 disputed by no one, and which no one 

 deemed to re([uire any proof, that "a 

 thing cannot act where it is not." * 

 With this weapon the Cartesians 

 waged a formidable war against the 

 theory of gravitation, which, accord- 

 ing to them, involving so obvious an 

 absurdity, must be rejected in limine : 

 the sun could not possibly act upon 

 the earth, not being there. It was 

 not surprising that the adherents of 

 the old systems of astronomy should 

 urge this objection against the new ; 

 but the false assumption imposed 

 equally on Newton himself, who, in 

 order to turn the edge of the objec- 

 tion, imagined a siibtle ether which 

 filled up the space between the sun 

 and the earth, and by its intermediate 

 agency was the proximate cause of 

 the phenomena of gravitation. " It 

 is inconceivable," said Newton, in one 

 of his letters to Dr. Bentley,t " that 

 inanimate brute matter should, with- 

 out the mediation of something else, 

 which is not material, operate upon 

 and affect other matter loithout mutual 

 contact. . . . That gravity should be 

 innate, inherent, and essential to mat- 

 ter, so that one body may act on 

 another at a distance, through a va- 

 cuum, without the mediation of any- 

 thing else, by and through which 

 their action and force may be con- 

 veyed from one to another, is to me 

 so great an absurdity, that I believe 

 no man, who in philosophical matters 

 has a competent faculty of thinking, 

 can ever fall into it." This passage 

 should be hung up in the cabinet of 

 every cultivator of science who is ever 

 tempted to pronounce a fact impos- 

 sible because it appears to him incon- 

 ceivable. In our own day one would 

 be more tempted, though with equal 

 injustice, to reverse the concluding 

 observation, and consider the seeing 



* It seems that this doctrine was, before 

 the time I have mentioned, disputed by 

 .<^ome thinkers. Dr. Ward mentions Scotns, 

 Va-sqiiez, Biel, Francis Lugo, and Valentiu. 



t I quote this passage from Playfair'.s 

 celebiated Dissertation on the Proijre-s of 

 Mathevmtical und J'hysical Science. 



