conceivability the supreme test as to what is knowable, Mr.
Spencer sets up a criterion which he himself violates. If it can be
shown that he places at the very foundation of Science a postulate or,
what is generally conceded to be a demonstrated truth, which, equally
with the conception of the Universe as self-existent, involves the
conception of infinite past-time, it is evident that we shall have
broken down the fundamental distinguishing characteristic which
separates his "Knowable" from his "Unknowable," and thus leave Science
and Religion standing upon the same level of validity in their relation
to the human mind. In the second part of "First Principles," which
treats of the "Knowable," Mr. Spencer says (p. 180): "The
Indestructibility of Matter ... is a proposition on the truth of which
depends the possibility of exact Science. Could it be shown, or could it
with any rationality be even supposed, that Matter, either in its
aggregates or in its units, ever became non-existent, there would be
need either to ascertain under what conditions it became non-existent,
or else to confess that Science and Philosophy are impossible. For if,
instead of having to deal with fixed quantities and weights, we had to
deal with quantities and weights which were apt, wholly or in part, to
be annihilated, there would be introduced an incalculable element, fatal
to all positive conclusions" (p. 172). Considering that in times past
men have believed in the creation of Matter out of nothing and in its
annihilation, he points out that it is to quantitative Chemistry that we
owe the empirical basis for our present belief.

Next he inquires "whether we have any higher warrant for this
fundamental belief than the warrant of conscious induction," and writes
as follows of logical necessity (pp. 172-179): "The consciousness of
logical necessity, is the consciousness that a certain conclusion is
implicitly contained in certain premises explicitly stated. If,
contrasting a young child and an adult, we see that this consciousness
of logical necessity, absent from the one is present in the other, we
are taught that there is a _growing up_ to the recognition of certain
necessary truths, merely by the unfolding of the inherited intellectual
forms and faculties. To state the case more specifically:--before a
truth can be known as necessary, two conditions must be fulfilled. There
must be a mental structure capable of grasping the terms of the
propo