FALLACIES OF SIMPLE INSPECTION. 525 



in supposing antipodes to be inconceivable, when present experience proves 

 that they can be conceived. Even if this objection were allowed, and the 

 proposition that what is inconceivable can not be true M'ere suffered to 

 remain unquestioned as a speculative truth, it would be a truth on which 

 no practical 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 inconceivable. Antipodes were really, not fictitiously, in- 

 conceivable to our ancestors: they are indeed conceivable to us; and as 

 the limits of our power of conception have been so largly extended, by the 

 extension of our experience and the more varied exercise of our imagina- 

 tion, so may posterity find many combinations perfectly conceivable to 

 them which are inconceivable to us. But, as beings of limited experience, 

 we must always and necessarily have limited conceptive powers ; while it 

 does not by any means follow that the same limitation obtains in the pos- 

 sibilities of Nature, nor even in her actual manifestations. 



Rather more than a century and a half ago it was a scientific maxim, 

 disputed by no one, and which no one deemed to require any proof, that 

 "a thing can not 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 ifi 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 adga of the objection, im- 

 agined a subtle ether Avhich filled up the space between the sun and the 

 earth, and by its intermediate agency was the proximate cause of the phe- 

 nomena of gravitation. " It is inconceivable," said Newton, in one of his 

 letters to Dr. Bentley,f " that inanimate brute matter should, without the 

 mediation of something else, which is not material, operate upon and affect 



other matter without mutual contact That gravity should be innate, 



inherent, and essential to matter, so that one body may act on another, at 

 a distance, through a vacuum, without the mediation of any thing else, by 

 and through which their action and force may be conveyed from one to 

 another, is to me so great an absurdity, that I believe no man, who in phil- 

 osophical 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 impossible because it 

 appears to him inconceivable. In our own day one would be more tempt- 

 ed, though with equal injustice, to reverse the concluding observation, and 

 consider the seeing any absurdity at all in a thing so simple and natural, 

 to be what really marks the absence of " a competent faculty of thinking." 

 No one now feels any difficulty in conceiving gi-avity to be, as much as 

 any other property is, *' inherent and essential to matter," nor finds the 

 comprehension of it facilitated in the smallest degree by the supposition 

 of an ether (though some recent inquirers do give this as an explanation 

 of it) ; nor thinks it at all incredible that the celestial bodies can and do 

 act where they, in actual bodily presence, are not. To us it is not more 

 wonderful that bodies should act upon one another " without mutual con- 

 tact," than that they should do so when in contact ; we are familiar with 



* It seems that this doctrine was, before the time I have mentioned, disputed by some 

 thinkers. Dr. Ward mentions Scotus, Vasquez, Biel, Francis Lugo, and Vajgptk. .^ 



t I quote this passage from Playfair's celebrated Dissertation on the Prqg^ess ^>f H^^t^iat- 

 ical and Physical Science. 



fx.) 



LIBRARY 



