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entitled The Correlation of Physical Forces , is cited (p. 53). It 
is true that the discussions in that work do point to some, bond of 
connection between the different physical forces of such kind that 
together with diversity in the modes of manifestation of the effects 
of the forces, there is unity as regards the intiinsic quality of the 
forces themselves. (This, for instance, would be the case if the 
different kinds of force might be supposed to be modes of pressure 
of a universally diffused elastic medium.) But I fail to see how 
facts and laws which indicate the existence, between physical forces, 
of relations depending on such unity , establish the reality of an 
abstract and necessary principle of continuity. The authors of lhe 
Unseen Universe make large use of such a principle, which, after 
having studied their applications of it, I can perceive to be nothing 
but Hume's principle of invariability of antecedence and con- 
sequence put in a new guise. Whether or not this be admitted, it 
is certain that this principle, equally with that of Hume, is opposed 
to regarding a miracle as an act determined exclusively by personal 
mil, and as incapable of being referred to antecedent conditions. 
This remark, which is clearly justified by the citations above given, 
is important as respects what I shall have, to say subsequently 
concerning the philosophy of The Unseen Universe. . 
12. I proceed now to state as distinctly as I can the principles of 
the philosophy which I have already spoken of as directly opposed 
to that of Hume. This philosophy received its chief development 
at the epoch of Locke and Newton. With respect to Newton s 
share in originating or unfolding its principles, I do not so much 
refer to the natural philosophy established by the propositions o 
the Principia (although this was a necessary preliminary), as to 
“ the Rules of Philosophizing’' which he gave at the beginning of 
the third book, and to the conclusions he has come to m the 
general Scholium at the end. It is there that we meet with 
Newton's metaphysical views respecting matter and force, agreeing 
in the main with those held by Locke. } 
13. In the following arguments I use the expression “ Newton^s 
Metaphysics,” or “ Physical Philosophy,' rather than Newton s 
Philosophy,'' to avoid ambiguity, as the latter. expression might be 
taken to include his theory of Universal Gravitation ; whereas, the 
subject I propose to discuss relates exclusively to the intrinsic 
qualities of matter and force. _ . 
Now the governing principle of the Newtonian metaphysics is, 
that there are no essential, or ultimate, qualities of matter and 
force, but such as we can understand by means of sensation and 
experience. This is a regulative principle,, proper for being em- 
ployed to determine what, according to this philosophy, are the 
