know it, is always some particular kind of matter. It must be
iron, brass, water, air, or other such. The difference between the
different kinds of matter is qualitative, that is to say, we know that
air is air because it has the qualities of air and differs from iron
because iron has the qualities of iron, and so on. The primeval matter
of Anaximander is just matter not yet sundered into the different
kinds of matter. It is therefore formless and characterless. And as it
is thus indeterminate in quality, so it is illimitable in quantity.
Anaximander believed that this matter stretches out to infinity
through space. The reason he gave for this opinion was, that if there
were a limited amount of matter it would long ago have been used up in
the creation and destruction of the "innumerable worlds." Hence he
called it "the boundless." In regard to these "innumerable worlds,"
the traditional opinion about Anaximander was that he believed these
worlds to succeed each other in time, and that first a world was
created, developed, and was destroyed, then another world arose, was
developed and destroyed, and that this periodic revolution of worlds
went on for ever. Professor Burnet, however, is of opinion that the
"innumerable worlds" of Anaximander were not necessarily successive but
rather simultaneously existing worlds. According to this view there
may be any number of worlds existing at the same time. But, even so,
it is still true that these worlds were not everlasting, but began,
developed and decayed, giving place in due time to other worlds.

How, now, have these various worlds been formed out of the formless,
indefinite, indeterminate matter of {26} Anaximander? On this question
Anaximander is vague and has nothing very definite to put forward.
Indeterminate matter by a vaguely conceived process separates itself
into "the hot" and "the cold." The cold is moist or damp. This cold
and moist matter becomes the earth, in the centre of the universe. The
hot matter collects into a sphere of fire surrounding the earth. The
earth in the centre was originally fluid. The heat of the surrounding
sphere caused the waters of the earth progressively to evaporate
giving rise to the envelope of air which surrounds the earth. For the
early Greeks regarded the air and vapour as the same thing. As this
air or vapour expanded under the action of heat it burst the outside
hot sphere of fire into a series of enormous "wheel-shaped husks,"
r