timaeus   

generation, moistened by water and inflamed by fire, and receiving the
forms of earth and air, and experiencing all the affections which
accompany these, presented a strange variety of appearances; and being
full of powers which were neither similar nor equally balanced, was
never in any part in a state of equipoise, but swaying unevenly hither
and thither, was shaken by them, and by its motion again shook them;
and the elements when moved were separated and carried continually,
some one way, some another; as, when rain is shaken and winnowed by
fans and other instruments used in the threshing of corn, the close
and heavy particles are borne away and settle in one direction, and
the loose and light particles in another. In this manner, the four
kinds or elements were then shaken by the receiving vessel, which,
moving like a winnowing machine, scattered far away from one another
the elements most unlike, and forced the most similar elements into
dose contact. Wherefore also the various elements had different places
before they were arranged so as to form the universe. At first, they
were all without reason and measure. But when the world began to get
into order, fire and water and earth and air had only certain faint
traces of themselves, and were altogether such as everything might
be expected to be in the absence of God; this, I say, was their nature
at that time, and God fashioned them by form and number. Let it be
consistently maintained by us in all that we say that God made them as
far as possible the fairest and best, out of things which were not
fair and good. And now I will endeavour to show you the disposition
and generation of them by an unaccustomed argument, which am compelled
to use; but I believe that you will be able to follow me, for your
education has made you familiar with the methods of science.
In the first place, then, as is evident to all, fire and earth and
water and air are bodies. And every sort of body possesses solidity,
and every solid must necessarily be contained in planes; and every
plane rectilinear figure is composed of triangles; and all triangles
are originally of two kinds, both of which are made up of one right
and two acute angles; one of them has at either end of the base the
half of a divided right angle, having equal sides, while in the
other the right angle is divided into unequal parts, having unequal
sides. These, then, proceeding by a combination of probability with
demonstration, we assume to be the original elements of fire and the
other bodies; but the principles which are prior to these God only
knows, and he of men who is the friend God. And next we have to
determine what are the four most beautiful bodies which are unlike one
another, and of which some are capable of resolution into one another;
for having discovered thus much, we shall know the true origin of
earth and fire and of the proportionate and intermediate elements. And
then we shall not be willing to allow that there are any distinct
kinds of visible bodies fairer than these. Wherefore we must endeavour
to construct the four forms of bodies which excel in beauty, and
then we shall be able to say that we have sufficiently apprehended
their nature. Now of the two triangles, the isosceles has one form
only; the scalene or unequal-sided has an infinite number. Of the
infinite forms we must select the most beautiful, if we are to proceed
in due order, and any one who can point out a more beautiful form than
ours for the construction of these bodies, shall carry off the palm,
not as an enemy, but as a friend. Now, the one which we maintain to be
the most beautiful of all the many triangles (and we need not speak of
the others) is that of which the double forms a third triangle which
is equilateral; the reason of this would be long to tell; he who
disproves what we are saying, and shows that we are mistaken, may
claim a friendly victory. Then let us choose two triangles, out of
which fire and the other elements have been constructed, one
isosceles, the other having the square of the longer side equal to
three times the square of the lesser side.
Now is the time to explain what was before obscurely said: there was
an error in imagining that all the four elements might be generated by
and into one another; this, I say, was an erroneous supposition, for