esembling cart wheels, which encircle the earth. You may naturally
ask how it is that if these are composed of fire we do not see them
continually glowing. Anaximander's answer was that these wheel-shaped
husks are encrusted with thick, opaque vapour, which conceals the
inner fire from our view. But there are apertures, or pipe-like holes
in the vapour-crust, and through these the fire gleams, causing the
appearance of the sun, stars, and moon. You will note that the moon
was, on this theory, considered to be fiery, and not, as we now know
it to be, a cold surface reflecting the sun's light. There were three
of these "cart wheels"; the first was that of the sun, furthest away
from the earth, nearer to us was that of the moon, and closest of all
was that of the fixed stars. The "wheel-shaped husks" containing the
heavenly bodies are revolved round the earth by means of currents of
air. The earth in the centre was believed by {27} Anaximander to be
not spherical but cylindrical. Men live on the top end of this pillar
or cylinder.

Anaximander also developed a striking theory about the origin and
evolution of living beings. In the beginning the earth was fluid and
in the gradual drying up by evaporation of this fluid, living beings
were produced from the heat and moisture. In the first instance these
beings were of a low order. They gradually evolved into successively
higher and higher organisms by means of adaptation to their
environment. Man was in the first instance a fish living in the water.
The gradual drying up left parts of the earth high and dry, and marine
animals migrated to the land, and their fins by adaptation became
members fitted for movement on land. The resemblance of this primitive
theory to modern theories of evolution is remarkable. It is easy to
exaggerate its importance, but it is at any rate clear that
Anaximander had, by a happy guess, hit upon the central idea of
adaptation of species to their environment.

The teaching of Anaximander exhibits a marked advance beyond the
position of Thales. Thales had taught that the first principle of
things is water. The formless matter of Anaximander is,
philosophically, an advance on this, showing the operation of thought
and abstraction. Secondly, Anaximander had definitely attempted to
apply this idea, and to derive from it the existent world. Thales had
left the question how the primal water developed into a world,
entirely unanswered.

Anaximenes