THEORY OF MATTER. 45 



fest, and on the other hand mechanical conceptions came to be 

 more developed, a new form of this system arose. The atoms, 

 retaining their forms and those which are commonly called 

 their primary qualities, were now supposed to act as centres 

 of attractive force, in other words, each atom was to the rest 

 a cause of motion. But as the ordinary "primary qualities" 

 of bodies may as we have seen be analysed into conceptions 

 which involve nothing beside motion and force, this new form 

 of the doctrine may clearly be considered merely as a state of 

 transition to that which is now known by the title of Boscovich's 

 theory *. To Boscovich appears to belong the credit of having 

 perceived that if the atoms were conceived of simply as unex- 

 tended centres of force the primary qualities of bodies might 

 sufficiently be accounted for without supposing them to result 

 from the primary qualities of their constituent atoms a mode 

 of explanation of which, though there has been something like 

 a return to it in some recent speculations, it may be observed 

 that it explains nothing. Boscovich's theory seems to have 

 been so completely in accordance with the direction in which 

 mathematical physics have of late been moving, that it was 

 adopted as it were unconsciously almost all modern investiga- 

 tions on subjects connected with molecular action are in effect 

 based on his views, though his name is, comparatively speaking, 

 but seldom mentioned. And this theory, (whether or not the 

 hypothesis of the existence of discrete centres of action be or be 

 not essential to it, a question connected with that which in 

 former times caused so much perplexity, namely, the nature of 

 continuity, and which it is not necessary to my present purpose 

 to consider), is in truth the highest developement which the 

 mathematical theory of matter has as yet received it is that on 

 which the pretensions of mathematical physicists to vindicate 

 for their own methods the right, so to speak, if not the power, to 

 explain all phenomena mainly depend. Adopting for the sake 

 of definite conception the received form of this theory, that 



* It is, I believe, known that Boscovich's fundamental idea was deduced by a 

 not unnatural filiation from the monadism of Leibnitz. Yet the scope and limits 

 which he proposed to himself differ essentially from those of the German phi- 

 losopher, inasmuch as they are essentially physical. Moreover, the latter would 

 have objected on the principle of sufficient reason to the want of any thing to indi- 

 viduate the atoms of Boscovich ; and, at least in the latter years of his life, to the 

 "Feme Wirkung," on which the whole theory depends. 



