The theory thus appeals directly to our experiences of the
behaviour of matter; and in deriving so little support as it does
from these experiences, it remains an essentially weak
speculation, whatever we may think of its ingenuity. For so long
as we are asked to accept conclusions drawn from our experiences
of the material world, we are justified in demanding something
more than mere unconditioned possibility. We require some
positive evidence, be it ever so little in amount; and no theory
which cannot furnish such positive evidence is likely to carry to
our minds much practical conviction.

This is what I meant by saying that the great weakness of the
hypothesis here criticized lies in its materialistic character.
In contrast with this we shall presently see that the assertion
of a future life which is not materially conditioned, though
unsupported by any item of experience whatever, may nevertheless
be an impregnable assertion. But first I would conclude the
foregoing criticism by ruling out altogether the sense in which
our authors use the expression "Unseen Universe." Scientific
inference, however remote, is connected by such insensible
gradations with ordinary perception, that one may well question
the propriety of applying the term "unseen" to that which is
presented to "the mind's eye" as inevitable matter of inference.
It is true that we cannot see the ocean of ether in which visible
matter floats; but there are many other invisible things which
yet we do not regard as part of the "unseen world." I do not see
the air which I am now breathing within the four walls of my
study, yet its existence is sufficiently a matter of
sense-perception as it fills my lungs and fans my cheek. The
atoms which compose a drop of water are not only invisible, but