26 The Poetry of Physics and The Physics of Poetry
were gods and goddesses. Anaxagoras was banished for his idea and
almost lost his life on its account. His idea was also rejected by Aristotle,
as were the concept of a void and the concept of human evolution.
Anaximander argued the case for human evolution almost 2500 years
before Darwin on the basis of his observations of the human embryo and
on the grounds that since the newborn human child is completely
helpless humans must have descended from a more primitive form of life
whose young are self-sufficient. Another biological conclusion reached
by the Ionian philosophers was their belief in the inherent healing power
of nature.
Of all these important discoveries perhaps the most important
contribution the Ionian physicists made to our intellectual heritage was
their idea that all matter of the universe was composed of a single
substance. Modern physics has shown that this is not the case, as
there are a number of elementary particles or quarks out of which the
elementary particles are composed. Still the concept of a universal such
as a primary substance was the precious gift of Greek thought. We shall
return to the question of why the concept of a universal arose among the
Greeks. For the moment let us review their various systems. Thales, the
originator of the concept, believed all matter was composed of water. His
disciple Anaximander believed that all things were composed of a neutral
substance he called apieron whose literal Greek meaning is infinite or
limitless. He believed that the various opposite such as hot and cold, dry
and wet, light and dark were all contained within this neutral substance
apieron and became separated to form the various substances observed in
nature. For Anaximenes the primary substance is air and the diversity of
matter is explained in terms of the varying densities of air. For example,
as air becomes thinner it becomes like fire and as it becomes denser it
turns from air to mist to dew to water to mud to earth to stone and so on.
What we know of the philosophical systems of Thales, Anaximander,
and Anaximenes does not come directly from their writings but rather
from the comments about their work by later authors such as Plato and
Aristotle. The first Ionian physicist-philosopher to have left a substantial
fragment of his writing behind is Heraclitus whose fascinating aphorisms
are still of philosophical, scientific, and literary interest.
His faith in the empirical method as well as his understanding of it are
attested to in the following aphorisms:
The things of which there can be sight, hearing and learning —
these are what I especially prized. Eyes are more accurate