His proof of this was a logical one; the absolutely self-existent could not
be thought in conjunction with attributes which either admitted any external
influencing Him, or any external influenced by Him. The prevailing dualism
he considered to be, as an ultimate theory of the universe, unthinkable and
therefore false. Outside the Self-existent there could be no second
self-existent, otherwise each would be conditioned by the existence of the
other, and the Self-existent would be gone. Anything different from the
Self-existent must be of the non-existent,
i.e. must be nothing.
One can easily see in these discussions some adumbration of many theological
or metaphysical difficulties of later times, as of the origin of evil, of
freewill in man, of the relation of the created world to its Creator. If
these problems cannot be said to be solved yet, we need not be surprised
that Xenophanes did not solve them. He was content to emphasise that which
seemed to him to be necessary and true, that God was God, and not either a
partner with, or a function of, matter.
At the same time he recognised a world of phenomena,
or, as he expressed it, a world of guesswork or opinion (δόξα).
As to the origin of things within this sphere he was ready enough to borrow
from the speculations of his predecessors. Earth and water are the sources
from which we spring; and he imagined a time when there was neither sea nor
land, but an all-pervading slough and slime; nay, many such periods of
inundation and emergence had been, hence the sea-shells on the tops of
mountains and the fossils in the rocks. Air and fire also as agencies of
change are sometimes referred to by him; anticipations in fact are visible
of the fourfold classification of the elements which was formally made by
some of his successors.