matter, in
man's case, by associating with matter a hypothetical substance, which
is in truth much less intelligible than matter itself. They regarded
themselves as double; a compound of matter and something else
miraculously united with it, to which they give the name of _mind_ or
_soul_, and then they proudly looked on themselves as beings apart from
the rest of creation. In plain truth, Mind is only an _occult force_,
invented to explain occult qualities and actions, and really explaining
nothing. By Mind they mean no more than the unknown cause of phenomena
that they cannot explain naturally, just as the Red Indians believed
that it was spirits who produced the terrible effects of gunpowder, and
just as the ignorant of our own day believe in angels and demons. How
can we figure to ourselves a form of being, which, though not matter,
still acts on matter, without having points of contact or analogy with
it; and on the other hand itself receives the impulsions of matter,
through the material organs that warn it of the presence of external
objects? How can we conceive the union of body and soul, and how can
this material body enclose, bind, constrain, determine a fugitive form
of being, that escapes every sense? To resolve these difficulties by
calling them mysteries, and to set them down as the effects of the
omnipotence of a Being still more inconceivable than the human Soul
itself, is merely a confession of absolute ignorance.

It is worth noticing that with the characteristic readiness of the
French materialist school to turn metaphysical and psychological
discussion to practical uses, Holbach discerned the immense new field
which the materialist account of mind opened to the physician. "If
people consulted experience instead of prejudice, medicine would furnish
morality with the key of the human heart; and in curing the body, it
would be often assured of curing the mind too.... The dogma of the
spirituality of the soul has turned morality into a conjectural science,
which does not in the least help us to understand the true way of acting
on men's motives.... Man will always be a mystery for those who insist
on regarding him with the prejudiced eyes of theology, and on
attributing his actions to a principle of which they can never have any
clear ideas" (ch. ix.). It is certainly true as a historical fact that
the rational treatment of insane persons, and the rational view of
certain kinds of crime, were due to men