have a knowledge of the necessity of that succession--and hence, of
necessary laws--and I, for my part, do not see what escape there is from
utter materialism and necessarianism. For it is obvious that our
knowledge of what we call the material world is, to begin with, at least
as certain and definite as that of the spiritual world, and that our
acquaintance with law is of as old a date as our knowledge of
spontaneity. Further, I take it to be demonstrable that it is utterly
impossible to prove that anything whatever may not be the effect of a
material and necessary cause, and that human logic is equally
incompetent to prove that any act is really spontaneous. A really
spontaneous act is one which, by the assumption, has no cause; and the
attempt to prove such a negative as this is, on the face of the matter,
absurd. And while it is thus a philosophical impossibility to
demonstrate that any given phenomenon is not the effect of a material
cause, any one who is acquainted with the history of science will admit,
that its progress has, in all ages, meant, and now, more than ever,
means, the extension of the province of what we call matter and
causation, and the concomitant gradual banishment from all regions of
human thought of what we call spirit and spontaneity.

I have endeavoured, in the first part of this discourse, to give you a
conception of the direction towards which modern physiology is tending;
and I ask you, what is the difference between the conception of life as
the product of a certain disposition of material molecules, and the old
notion of an Archaeus[54] governing and directing blind matter within
each living body, except this--that here, as elsewhere, matter and law
have devoured spirit and spontaneity? And as surely as every future
grows out of past and present, so will the physiology of the future
gradually extend the realm of matter and law until it is co-extensive
with knowledge, with feeling, and with action.