not a positive ground of belief. If the
hypothesis of self-evolution is true, we should _a priori_ expect that by
the time evolution had advanced sufficiently far to admit of the production
of a reasoning intelligence, the complexity of nature must be so great that
the nascent reasoning powers would be completely baffled in their attempts
to comprehend the various processes going on around them. This seems to be
about the state of things which we now experience. Still, as reason
advances more and more, we may expect, both from general _a priori_
principles and from particular historical analogies, that more and more of
the processes of nature will admit of being interpreted by reason, and that
in proportion as our ability to _understand_ the frame and the constitution
of things progresses, so our ability to _conceive_ of them as all naturally
and necessarily evolved will likewise and concurrently progress. Thus, for
example, how vast a number of the most intricate and delicate correlations
in nature have been rendered at once intelligible and conceivably due to
non-intelligent causes, by the discovery of a single principle in
nature--the principle of natural selection.

'In the adverse argument, conceivability is again made the unconditional
test of truth, just as it was in the argument against the possibility of
matter thinking. We reject the hypothesis of self-evolution, not because it
is the more remote one, but simply because we experience a subjective
incapacity adequately to frame the requisite generalisations in thought, or
to frame them with as much clearness as we could wish. Yet our reason tells
us as plainly as it tells us any general truth which is too large to be
presented in detail, that there is nothing in the nature of things
themselves, as far as we can see, antagonistic to the supposition of their
having been self-evolved. Only on the ground, therefore, of our own
intellectual deficiencies; only because as yet, by the self-evolutionary
hypothesis, the inner order does not completely answer to the outer order;
only because the number and complexity of subjective relations have not yet
been able to rival those of the objective relations producing them; only on
this ground do we refuse to assent to the obvious deductions of our
reason.[29]

'And here I may observe, further, that the presumption in favour of atheism
which these deductions establish is considerably fortified by certain _a
posteriori_ consid