ACTION AT A DISTANCE. 315 



maintain the doctrine, founded only on the rough experience of a pre-scientific 

 age, that matter cannot act where it is not, instead of admitting that all the 

 facts from which our ancestors concluded that contact is essential to action were 

 in reality cases of action at a distance, the distance being too small to be 

 measured by their imperfect means of observation ? 



If we are ever to discover the laws of nature, we must do so by obtaining 

 the most accurate acquaintance with the facts of nature, and not by dressing 

 up in philosophical language the loose opinions of men who had no know- 

 ledge of the facts which throw most light on these laws. And as for those 

 who introduce setherial, or other media, to account for these actions, without 

 any direct evidence of the existence of such media, or any clear understanding 

 of how the media do their work, and who fill all space three and four times 

 over with aethers of different sorts, why the less these men talk about their 

 philosophical scruples about admitting action at a distance the better. 



If the progress of science were regulated by Newton's first law of motion, 

 it would be easy to cultivate opinions in advance of the age. We should only 

 have to compare the science of to-day with that of fifty years ago ; and by 

 producing, in the geometrical sense, the line of progress, we should obtain the 

 science of fifty years hence. 



The progress of science in Newton's time consisted in getting rid of the 

 celestial machinery with which generations of astronomers had encumbered the 

 heavens, and thus " sweeping cobwebs off the sky." 



Though the planets had already got rid of their crystal spheres, they were 

 still swimming in the vortices of Descartes. Magnets were surrounded by 

 effluvia, and electrified bodies by atmospheres, the properties of which resembled 

 in no respect those of ordinary effluvia and atmospheres. 



When Newton demonstrated that the force which acts on each of the 

 heavenly bodies depends on its relative position with respect to the other 

 bodies, the new theory met with violent opposition from the advanced philoso- 

 phers of the day, who described the doctrine of gravitation as a return to the 

 exploded method of explaining everything by occult causes, attractive virtues, 

 and the like. 



Newton himself, with that wise moderation which is characteristic of all his 

 speculations, answered that he made no pretence of explaining the mechanism 

 by which the heavenly bodies act on each other. To determine the mode in 

 which their mutual action depends on their relative position was a great step 



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