reason for speaking of it as "immaterial" or "spiritual."
Though we are unable to weigh it in the balance, we at least know it as
a transmitter of undulatory movements, the size and shape of which we
can accurately measure. Its force-relations with ponderable matter are
not only universally and incessantly maintained, but they have that
precisely quantitative character which implies an essential identity
between the innermost natures of the two substances. We have seen
reason for thinking it probable that ether and ordinary matter are alike
composed of vortex-rings in a quasi-frictionless fluid; but whatever be
the fate of this subtle hypothesis, we may be sure that no theory
will ever be entertained in which the analysis of ether shall require
different symbols from that of ordinary matter. In our authors' theory,
therefore, the putting on of immortality is in no wise the passage from
a material to a spiritual state. It is the passage from one kind
of materially conditioned state to another. 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 othe