CHAP. XIV.] SCIENCE AND FREE WILL. 437 



as lie receives it from the authorities, is exactly that of 

 Descartes ; and if he has added to it another essential 

 function, namely thought, the new ingredient does not inter- 

 fere with the old, and certainly does not bring the matter of 

 Descartes into closer resemblance with that of Newton. 



The influence of the physical ideas of Newton on philoso- 

 phical thought deserves a careful study. It may be traced 

 in a very direct way through Maclaurin and the Stewarts to 

 the Scotch School, the members of which had all listened to 

 the popular expositions of the Newtonian Philosophy in their 

 respective colleges. In England, Boyle and Locke reflect 

 Newtonian ideas with tolerable distinctness, though both 

 have ideas of their own. Berkeley, on the other hand, 

 though he is a master of the language of his time, is quite 

 impervious to its ideas. Samuel Clarke is perhaps one of the 

 best examples of the influence of Newton ; while Eoger Cotes, 

 in spite of his clever exposition of Newton's doctrines, must 

 be condemned as one of the earliest heretics bred in the 

 bosom of Newtonianism. 



It is absolutely manifest from these and other instances 

 that any development of physical science is likely to pro- 

 duce some modification of the methods and ideas of philoso- 

 phers, provided that the physical ideas are expounded in such 

 a way that the philosophers can understand them. 



The principal developments of physical ideas in modern 

 times have been 



1st. The idea of matter as the receptacle of momentum 

 and energy. This we may attribute to Galileo and some of 

 his contemporaries. This idea is fully expressed by Newton, 

 under the form of Laws of Motion. 



2d. The discussion of the relation between the fact of 

 gravitation and the maxim that matter cannot act where it 

 is not. 



3d. The discoveries in Physical Optics, at the beginning 

 of this century. These have produced much less effect out- 

 side the scientific world than might be expected. There are 

 two reasons for this. In the first place it is difficult, especi- 

 ally in these days of the separation of technical from popular 



