tre of our system produces; and,
as we have already seen, the earth is to no small extent its own
sun--its own source of heat. The prospect thus opened out by modern
physical inquiry supports more strongly than ever the conviction that
the life of this world to come will be very prolonged. It is true that
there is always the possibility of accident. Encountering another globe,
our sun would doubtless produce so much heat as to incinerate all
planetary life. But the excessive remoteness of the sun from the nearest
fixed star suggests that the constitution of the stellar universe is
such that an accident of this kind is extremely improbable. As for
comets, the earth's atmosphere has already encountered a comet, even
during the brief period of astronomical observation. This thick overcoat
of ours protects us from the danger of such chances.

What, then, is the record? We are told that the belief in progress is a
malady of youth, which experience and the riper mind will dissipate.
Some such argument from the lips of the disillusioned or the
disidealized has been possible, perhaps, with some measure of
probability, until within our own times. They must now forever hold
their peace. We know as surely as we know the elementary phenomena of
physics or chemistry, that the record of life upon our planet, though
not only a record of progress by any means, has nevertheless included
that to which the name of progress cannot be denied in any possible
definition of the word. For myself, I understand by progress _the
emergence of mind, and its increasing dominance over matter_. Such
categories are, no doubt, unphilosophical in the ultimate sense, but
they are proximately convenient and significant. Now, if progress be
thus defined, we can see for ourselves that life has truly advanced, not
merely in terms of anatomical or physiological--_i. e._ mechanical or
chemical--complexity, but in terms of mind. The facts of nutrition teach
us that the first life upon the earth was vegetable; and though the
vegetable world displays great complexity, and that which, on some
definitions, would be called progress, yet we cannot say that there is
any more mind, any greater differentiation or development of sentience,
in the oak than in the alga. When we turn, however, to the animal
world--which is parasitic, indeed, upon the vegetable world--we find
that in what we may call the main line of ascent there has been, along
with increasing anatomical comp