same condition as ours. But it would be, or rather it
_is_, as unreasonable for men to maintain such an opinion now, when the
laws of planetary development are understood, when the various
dimensions of the planets are known, and when the shortness of the
life-supporting period of a planet's existence compared with the entire
duration of the planet has been clearly recognised, as it would be for
the imagined inhabitants of a small fruit on a tree to suppose that all
the other fruits on the tree, though some manifestly far less advanced
in development and others far more advanced than their own, were the
abode of the same forms of life, though these forms were seen to require
those conditions, and no other, corresponding to the stage of
development through which their own world was passing.

Viewing the universe of suns and worlds in the manner here suggested, we
should adopt a theory of other worlds which would hold a position
intermediate between the Brewsterian and the Whewellite theories. (It is
not on this account that I advocate it, let me remark in passing, but
simply because it accords with the evidence, which is not the case with
the others.) Rejecting on the one hand the theory of the plurality of
worlds in the sense implying that all existing worlds are inhabited, and
on the other hand the theory of but one world, we should accept a theory
which might be entitled the Paucity of Worlds, only that relative not
absolute paucity must be understood. It is absolutely certain that this
theory is the correct one, if we admit two postulates, neither of which
can be reasonably questioned--viz., first, that the life-bearing era of
any world is short compared with the entire duration of that world; and
secondly, that there can have been no cause which set all the worlds in
existence, not simultaneously, which would be amazing enough, but (which
would be infinitely more surprising) in such a way that after passing
each through its time of preparation, longer for the large worlds and
shorter for the small worlds, they all reached at the same time the
life-bearing era. But quite apart from this antecedent probability,
amounting as it does to absolute certainty if these two highly probably
postulates are admitted, we have the actual evidence of the planets we
can examine--that evidence proving incontestably, as I have shown
elsewhere, that such planets as Jupiter and Saturn are still in the
state of preparation, still so inten