PRIMARY CONCEPTS OF MODERN SCIENCE. 351 



considered as resisting the communication of motion." As is readily- 

 seen, all these definitions imply, nevertheless, that matter can be moved 

 or changed only from without, by forces external to matter itself. 

 Newton expressly (" Principia," Definitio IV.) speaks of force as 

 " impressed upon a body, and as exerted upon it to change its state of 

 rest or uniform motion in a straight line." 



There is little difficulty in understanding how this language, in con- 

 nection with the etymological import of the word "inertia," led to the 

 assumption that matter is essentially passive, or, as it is commonly 

 expressed, dead. There are other reasons for this assumption, con- 

 nected with the evolution, not only of scientific concepts, properly so 

 called, but of cosmological ideas, to which I shall have occasion, per- 

 haps, to recur in the sequel ; indeed, Newton's definitions which I 

 have just cited are simply instances of the intellectual postulates of 

 his time. And the mathematical treatment of mechanical problems, 

 from the nature of its methods, necessitates the fiction that force and 

 mass are separate and distinct terms. In general, it may be said that 

 the assumption of the absolute passivity of matter is one of those errors 

 which are inevitable in the progress of knowledge — one of the " clay 

 moulds in which the bells of scientific truth are cast." But the perpet- 

 uation of this error is one of the most fatal impediments to real scien- 

 tific progress in our day, and is fruitful of vagaries which are wholly 

 incommensurable with the real state of modern scientific knowledge. 

 Thus, Prof. Philip Spiller, the author of a very serviceable manual of 

 physics, and a prolific writer on scientific subjects, has recently pub- 

 lished a cosmological treatise, 1 whose theorems are founded upon the 

 express proposition {op. cit., p. 4) that " no material constituent of a 

 body, no atom, is in itself originally endowed with force, but that every 

 such atom is absolutely dead, and without any inherent power to act 

 at a distance." It appears from the further contents of Spiller's 

 treatise, that he not only denies force to the atoms taken singly, but 

 that he also denies the possibility of their mutual action. He is driven, 

 therefore, to the assertion of the independent substantiality of force; 

 and, accordingly, he assumes force to be an all-pervading #w<m-mate- 

 rial presence — as he terms it, an " incorporeal matter" {unkoerperlicher 

 Staff). In utter disregard of the fundamental correlation of force and 

 mass, Spiller identifies his force-substance with the ordinary luminif- 

 erous ether, so that this phantom, which, in the view of other physicists, 

 is not only imponderable, but destitute of cohesive, chemical, thermal, 

 electric, and magnetic forces (which, indeed, must be destitute of them 

 if it is to serve as the mere substratum of these various modes of mo- 

 tion) — which therefore is, if possible, still more " dead " than ordinary 

 ponderable matter — now suddenly, without changing its name, and 

 without ceasing to be the substratum of luminar and other undulations, 

 comes to be the very quintessence of all possible energy. 



1 "Der Weltaether als Kosmische Kraft," Berlin, Denicke's Yerlag, 1873. 



