er beings. Secondly, it is not as if terrestrial life formed a
scale, and celestial beings were all on a par, having among themselves
no {305} scale of higher and lower. This is not the case. The heavenly
bodies have grades among themselves. The higher are related to the
lower as form to matter. Thus stars are higher than planets. So that
if we suppose that evolution stops at man, what we have is a gap in
the middle, a scale below it, and a scale above it. It is like a
bridge over a sheet of water, the two ends of which are intact, but
which is broken down in the middle. The natural completion of this
scheme involves the filling up of the gap. Thirdly, we have another
very important piece of evidence. With his valuable idea of evolution
Aristotle combined another very curious, and no doubt, absurd, theory.
This was that in the scale of the universe the lowest existence is to
be found in the middle, the highest at the periphery, and that in
general the higher is always outside the lower, so that the spatial
universe is a system of concentric spheres, the outer sphere being
related to the inner sphere as higher to lower, as form to matter. At
the centre of the spherical universe is our earth. Earth, as the
lowest element, is in the middle. Then comes a layer of water, then of
air, then of fire. Among the heavenly bodies there are fifty-six
spheres. The stars are outside the planets and are therefore higher
beings. And in conformity with this scheme, the supreme being, God, is
outside the outermost sphere. Now it is obvious that, in this scheme,
the passage from the centre of the earth to the stars forms a spatial
continuity, and it is impossible to resist the conclusion that it also
forms a logical continuity, that is, that there is no break in the
chain of evolution.

Noting that this is not what Aristotle in so many words says, but that
it is our interpretation of his {306} intention, which is almost
certainly correct, we conclude that man is not the top of the scale.
Next to him come the heavenly bodies. The planets include the sun and
the moon, which, revolve round the earth in a direction opposite to
that of the stars. Next in the scale come the stars. We need not go
into details of the fifty-six spheres. The stars and planets are
divine beings. But this is only a comparative term. Man, as the
possessor of reason, is also divine, but the heavenly bodies
infinitely more so. And this means that they are more rational t