n with a
ghost. These phases, taken in their abstraction, as they first forced
themselves on human attention, have been taken for independent and
separable facts. Experience, remaining in both provinces quite sensuous
and superficial, has accordingly been allowed to link this purely mental
event with that purely mechanical one. The linkage is practically not
deceptive, because mental transformations are indeed signs of changes in
bodies; and so long as a cause is defined merely as a sign, mental and
physical changes may truly be said to cause one another. But so soon as
this form of augury tries to overcome its crude empiricism and to
establish phenomenal laws, the mental factor has to fall out of the
efficient process and be represented there by what, upon accurate
examination, it is seen to be really the sign of--I mean by some
physiological event.

If philosophers of the Cartesian school had taken to heart, as the
German transcendentalists did, the _cogito ergo sum_ of their master,
and had considered that a physical world is, for knowledge, nothing but
an instrument to explain sensations and their order, they might have
expected this collapse of half their metaphysics at the approach of
their positive science: for if mental existence was to be kept standing
only by its supposed causal efficacy nothing could prevent the whole
world from becoming presently a _bete-machine._ Psychic events have no
links save through their organs and their objects; the function of the
material world is, indeed, precisely to supply their linkage. The
internal relations of ideas, on the other hand, are dialectical; their
realm is eternal and absolutely irrelevant to the march of events. If we
must speak, therefore, of causal relations between mind and body, we
should say that matter is the pervasive cause of mind's distribution,
and mind the pervasive cause of matter's discovery and value. To ask for
an efficient cause, to trace back a force or investigate origins, is to
have already turned one's face in the direction of matter and mechanical
laws: no success in that undertaking can fail to be a triumph for
materialism. To ask for a justification, on the other hand, is to turn
no less resolutely in the direction of ideal results and actualities
from which instrumentality and further use have been eliminated. Spirit
is useless, being the end of things: but it is not vain, since it alone
rescues all else from vanity. It is called practical