process of retrogressive metamorphosis which might
eventually give me a place among the respectabilities. The prospect,
perhaps, ought to have pleased me; but I confess I felt something of
the uneasiness of the tailor who said that, whenever a customer's
circumference was either much less, or much more, than at the last
measurement, he at once sent in his bill; and I was not consoled until
I recollected that, thirteen years ago, in discussing Hume's essay on
"Miracles," I had quoted, with entire assent, the following passage
from his writings: "Whatever is intelligible and can be distinctly
conceived implies no contradiction, and can never be proved false by
any demonstrative argument or abstract reasoning _a priori_."[47]

Now, it is certain that the existence of demons can be distinctly
conceived. In fact, from the earliest times of which we have any record
to the present day, the great majority of mankind have had extremely
distinct conceptions of them, and their practical life has been more or
less shaped by those conceptions. Further, the notion of the existence
of such beings "implies no contradiction." No doubt, in our experience,
intelligence and volition are always found in connection with a certain
material organisation, and never disconnected with it; while, by the
hypothesis, demons have no such material substratum. But then, as
everybody knows, the exact relation between mental and physical
phenomena, even in ourselves, is the subject of endless dispute. We may
all have our opinions as to whether mental phenomena have a substratum
distinct from that which is assumed to underlie material phenomena, or
not; though if any one thinks he has demonstrative evidence of either
the existence or the non-existence of a "soul," all I can say is, his
notion of demonstration differs from mine. But, if it be impossible to
demonstrate the non-existence of a "substance" of mental phenomena--that
is, of a soul--independent of material "substance"; if the idea of such
a "soul" is "intelligible and can be distinctly conceived," then it
follows that it is not justifiable to talk of demons as
"impossibilities." The idea of their existence implies no more
"contradiction" than does the idea of the existence of pathogenic
microbes in the air. Indeed, the microbes constitute a tolerably exact
physical analogue of the "powers of the air" of ancient belief.

Strictly speaking, I am unaware of any thing that has a right to the
title o