364 POPULAR SCIENCE MONTHLY. 



in so far as it was universal. Otherwise it presents few qualities to 

 which we should attach this name at present. For the system con- 

 templated the division of matter into separate parts, each of which 

 occupied a place — a place subject to change, no doubt — in empty 

 space, while to these circling orbs force was linked somehow. The 

 relation between any two, therefore, can not be the result of inherent 

 nature, but must follow from the interference of a cause external to the 

 terms of the relation. Newton has put himself on decided record on 

 this very question. In a letter to Bentley, written about the new year 

 of 1693, he says: "It is inconceivable that inanimate brute matter 

 should, without the mediation of something else, which is not material, 

 operate upon and effect other matter without mutual contact, as it 

 must be, if gravitation, in the sense of Epicurus, be essential and in- 

 herent 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 the other, is to me so great an absurdity that I believe no man, 

 who has in philosophical matters a competent faculty of thinking, 

 can ever fall into it. Gravity must be caused by an agent acting con- 

 stantly according to certain laws; but whether this agent be material 

 or immaterial, I have left to the consideration of my readers." Sum- 

 marily put, this means that the solar system is the type of universe, 

 and it is a system, because 'an agent acting constantly according to 

 certain laws' has rendered it such. And this implies, further, that, 

 while a description of the universe may be possible, as in terms of 

 mathematics, an explanation of it is beyond reach. 



Turning to the philosophical side, a curious parallelism attracts 

 notice at once. Of course, we are dealing no longer with 'heavenly 

 bodies,' but matter and mind are treated by the philosophers exactly as 

 Newton dealt with his material wholes. Descartes asks himself in 

 effect. How is it that thought, which possesses none of the qualities 

 of extension (matter) and extension, which possesses none of the quali- 

 ties of thought, comes to unite so as to &e a single whole in man's ex- 

 perience? He supposes that ideas are copies of things. But, even 

 so. How do we know that the copies are correct or reasonably ade- 

 quate? The solution can come by one answer alone. Some agent, 

 which is neither an idea nor a thing, must vouch for the correspond- 

 ence. Just as, in the physical world, one body can not affect another, 

 except by the operation of a law-giving agent, so thought and extension 

 can not be combined in our universe, except God have so willed it. The 

 parallelism is precise. A 'third thing,' belonging neither to the sphere 

 of intellect nor to that of the external world, must be assumed as the 



