314 
of Mathematics and Physics,” which was published in 1869 ; and in a smaller 
work, entitled “ An Essay on the Mathematical Principles of Physics,” 
published in 1873.) . 
5. I am now prepared to indicate in what respect the Newtonian 
philosophy, legitimately employed, contradicts the assumption that phe- 
nomena can only be accounted for on the principle of mere antecedence and 
consequence according to law, and that, consequently, it is not possible to 
understand causes. From what is argued above, it will be seen thatm 
direct contravention of that assumption, Newton’s philosophy admits of t e 
existence of no coyisequence the relation of which to an antecedent cause is 
not cognisable from common sensation and experience. If we had no other 
sense than that of sight, we might conclude that matter is capable of 
moving matter without the agency of an intervening substance. But the 
sense of touch, and our consciousness of will and power, enable us to 
perceive that matter is acted upon by the pressure of other matter m contact 
with it, and according to the principles of a philosophy which refers all 
knowledge to personal sensation and experience, no other mode of action is 
admissible. 
6. It is true, however, that thus we do not account for t le exis ence 
the ffither, the atoms, and the simpler substances composed of atoms, nor lor 
their respective inherent qualities ; because, in fact, these entities constitute 
the foundation of the philosophy. The property of pressing proportionally 
to its density, which was considered (in Article 3) to belong to the aether, , is 
quite intelligible from what we know of the sensible properties of visib o 
and tangible fluids, in certain of which (as air of given temperature) the 
law actually exists. Now, although in the case of such bodies this law ot 
pressure might be shown to be due to dynamical action of the aether, 
inasmuch as all the physical forces (as already argued in Artie e ) are o 
be regarded as modes of its pressure, there is no need to seek for an analogous 
reason for the same law as respects the aether itself, because the hypothesis 
of this property is necessary as a foundation for applying mathematics to 
calculate its motions ; and the law, so far as it pertains to the aether, may 
be considered to be an ultimate fact. . , 
7. Accordingly, there are two kinds of physical realities that human mtel- 
ligence is capable of taking cognisance of,— those which as ultimate elements 
or facts constitute the basis of all physical phenomena, and those which are 
produced from these by causes operating according to ascertainable laws, 
is evident that the first kind admit of inquiry only as to their qualities, not 
as regards any antecedent producing cause ; whereas the other kind are 
proper subjects of human investigation, both as to the causes producing 
them, and as to the laws or modes of operation of the causes. The one kind, 
as having no antecedents, only give evidence of creative power ; the other as 
consisting of antecedents and consequents, the relations between which are 
such as we can understand, furnish proofs to us of intelligence and wisdom 
The intelligence is of the same kind, however different m degree, as th 
which the working of a machine which accomplishes in an intelligible mann 
