h so, perhaps, as any
generation in the history of the world. Within the last thirty
years the great wave of spiritualistic or idealistic thought ...
has been receding and decreasing; and another, which is in the main
driven by materialistic forces, has been gradually rising behind,
vast and threatening. It is but its crest that we at present see;
it is but a certain vague shaking produced by it that we at present
feel; but we shall probably soon enough fail not both to see and
feel it fully and distinctly[4].'

Such being the present importance of Materialism, I shall devote the
present chapter to a consideration of this theory. Each of the points in
the argument for Materialism which I have mentioned above admits, of
course, of elaboration; but I think that their enumeration contains all
that is essential to the theory in question. It now devolves upon us to
inquire whether this theory is adequate to meet the facts.

And here I may as well at once give it as my own opinion that, of
however much service the theory of Materialism may be, up to a certain
point, it can never be accepted by any competent mind as a final
explanation of the facts with which it has to deal. Unquestionable as
its use may be as a fundamental hypothesis in physiology and medicine,
it is wholly inadequate as a hypothesis in philosophy. That is to say,
so long as there is a constant relation of concomitancy found by
experience to obtain between neural processes and mental processes, so
long no harm can accrue to physical science by assuming, for its own
purposes, that this relation is a causal one. But as soon as the
question concerning the validity of this assumption is raised into the
region of philosophy, it receives the answer that the assumption cannot
be allowed to pass. For where the question becomes one not as to the
_fact_ of the association but as to its _nature_, philosophy, which must
have regard to the facts of mind no less than to those of matter, must
pronounce that the hypothesis is untenable; for the hypothesis of this
association being one of causality acting from neurosis to psychosis,
cannot be accepted without doing violence, not merely to our faculty of
reason, but to our very idea of causation itself.

A very small amount of thinking is enough to show that what I call my
knowledge of the external world, is merely a knowledge of my own mental
modifications. A step further and I find t