Letter to Lord Brougham. 479 



philosophy, — the reduction of all that is implied in the terms 

 space, force, and matter, to the closest relations and the fewest 

 agencies : he regarded this great discovery with no more par- 

 tiality than he did the more undeveloped principle of molecu- 

 lar cohesion, with respect to which, after stating his general 

 conception of the force, he comes to this conclusion — "there 

 are therefore agents in nature able to make the particles of 

 bodies stick together by very strong attractions; and it is the 

 business of experimental philosophy tojind them out*." 



The term attraction) be it observed, was always employed by 

 Newton in a provisional sense. " How these attractions may 

 be performed," he says, " I do not here consider: what I call 

 attraction may be performed by impulse, or by some other 

 means unknown to me; I use that word here to signify only 

 in general any force by which bodies tend towards each other, 

 whatsoever be the cause:" thus he was content to express, in 

 any terms that lay at hand, the mathematical law, whilst he 

 kept the efficient cause in reserve, laying down for the order 

 of investigation this rule — " We must learn from the phaeno- 

 mena of nature what bodies attract one another, and what are 

 the laws and properties of the attraction, before we inquire 

 the cause by which the attraction was performed t." 



The cause of gravity, whatever it may bd he conceived must 

 also lie at the foundation of all the other great classes of force 

 which we observe, and till their laws and properties should 

 have been iearnt, he knew that it would be premature to at- 

 tempt any deep inquiry into their causes. Nevertheless he 

 let loose his fancy in more than one excursion into this wide 

 field of speculation ; and it is worth our while to mark the 

 manner in which he surveyed it. For he possessed beyond 

 other men that double power of mind which can adapt itself 

 equally to the furthest and nearest limits of vision, and cast a 

 glance as comprehensive over remote objects, as precise and 

 penetrating into those that are within reach. 



The widest of the generalisations to which the conjectures 

 of Newton ascended were marked by a character far different 

 from any which appears in the speculations of those who pre- 

 ceded him. Instead of loose or narrow analogies, in forming 

 his ideas of the interior mechanism and materials of the uni- 

 verse, he clothed the phantoms of his philosophical vision with 

 the most certain and general of the properties of matter: 

 for the hooked atoms of Epicurus, the broken fragments, 

 subtle powder, rounded globules, and feathery filaments of 

 Descartes, he substituted the conception of particles embody- 

 ing invariable powers of inertia, solidity, and hardness, with 

 * Optics, Book 3. Qu. 31. t Ibid. 



