340 



SCIENTIFIC THOUGHT. 



could be traced. 1 What to some contemporaries of Newton, 

 and even to Newton himself, seemed an absurdity that 

 action could take place at a distance 2 became through 



1 Voltaire, who did not dive very 

 deep into the teachings of Newton, 

 gives a graphic description of the 

 different opinions then current in 

 English and French learned circles. 

 In his ' Lettres sur les Anglais,' 

 written about the time of the death 

 of Newton, after having discoursed 

 on Quakerism, the Church and 

 Government, on vaccination, Bacon 

 and Locke, he devotes four chapters 

 to the philosophy of Newton, which 

 he contrasts with that of Descartes. 

 " Un Franfais qui arrive a Londres 

 trouve les choses bien changers en 

 philosophic, comme dans tout le 

 reste. II a laisse" le monde plein, il 

 le trouve vide. A Paris on voit 

 1'univers compost de tourbillons de 

 matiere subtile, a Londres on ne 

 voit rien de cela. Chez nous c'est 

 la pression de la lune qui cause le 

 flux de la mer ; chez les Anglais 

 c'est la mer qui gravite vers la 

 lune. . . . Chez vos Carte"siens 

 tout se fait par une impulsion qu'on 

 ne comprend guere ; chez M. New- 

 ton c'est par une attraction dont on 

 ne connait pas mieux la cause. . . . 

 Descartes assure encore que 1'e'ten- 

 due seule fait la matiere, Newton y 

 ajoute la solidite " (lettre xiv. ) 



2 " You sometimes speak of grav- 

 ity as essential and inherent to 

 matter. Pray, do not ascribe that 

 notion to me ; for the cause of grav- 

 ity is what I do not pretend to 

 know " (Newton's 2d letter to Bent- 

 ley, 17th January 1692-93). "It 

 is inconceivable that inanimate brute 

 matter should, without the media- 

 tion of something else, which is not 

 material, operate upon and affect 

 other matter without mutual con- 

 tact, as it must be, if gravitation, 

 in the sense of Epicurus, be essential 

 and inherent in it. And this is one 



reason why I desired you would not 

 ascribe innate gravity to me. That 

 gravity should be innate, inherent, 

 and essential to matter, so that one 

 body may act upon another at a 

 distance through a vacuum, without 

 the mediation of anything else, by 

 and through which their action and 

 force may be conveyed from one to 

 another, is to me so great an ab- 

 surdity that I believe no man, who 

 has in philosophical matters a com- 

 petent faculty of thinking, can ever 

 fall into it. Gravity must be caused 

 by an agent acting constantly ac- 

 cording to certain laws ; but whether 

 this agent be material or immaterial, 

 I have left to the consideration of 

 my readers " (3d letter to Bentley, 

 5th February 1692-93). And in 

 the fifth answer to Leibniz (pub- 

 lished after Leibniz's death) Clarke 

 says : " That the sun attracts the 

 earth . . . that is, that the earth 

 and sun gravitate towards each 

 other, or tend towards each other, 

 with a force which is in a direct 

 proportion of their masses, . . . 

 and in an inverse duplicate propor- 

 tion of their distances, and that the 

 space betwixt them is void that is, 

 has nothing in it which sensibly re- 

 sists the motion of bodies passing 

 transversely through : all this is 

 nothing but a phenomenon or actual 

 matter of fact, found by experience. 

 That this phenomenon is not pro- 

 duced sans moyen that is, without 

 some cause capable of producing 

 such an effect is undoubtedly true. 

 Philosophers therefore may search 

 after and discover that cause, if 

 they can ; be it mechanical or not 

 mechanical. . . . The phenomenon 

 itself, the attraction, gravitation, or 

 tendency of bodies towards each 

 other, and the laws or proportions 



