On The Heavens
same thing happens again when the residue produces water. But this can
only go on for ever, if the finite body contains an infinity, which is
impossible. Therefore the generation of elements out of one another
will not always continue.
(2) We have now explained that the mutual transformations of the
elements cannot take place by means of excretion. The remaining
alternative is that they should be generated by changing into one
another. And this in one of two ways, either by change of shape, as
the same wax takes the shape both of a sphere and of a cube, or, as
some assert, by resolution into planes. (a) Generation by change of
shape would necessarily involve the assertion of atomic bodies. For if
the particles were divisible there would be a part of fire which was
not fire and a part of earth which was not earth, for the reason
that not every part of a pyramid is a pyramid nor of a cube a cube.
But if (b) the process is resolution into planes, the first difficulty
is that the elements cannot all be generated out of one another.
This they are obliged to assert, and do assert. It is absurd,
because it is unreasonable that one element alone should have no
part in the transformations, and also contrary to the observed data of
sense, according to which all alike change into one another. In fact
their explanation of the observations is not consistent with the
observations. And the reason is that their ultimate principles are
wrongly assumed: they had certain predetermined views, and were
resolved to bring everything into line with them. It seems that
perceptible things require perceptible principles, eternal things
eternal principles, corruptible things corruptible principles; and, in
general, every subject matter principles homogeneous with itself.
But they, owing to their love for their principles, fall into the
attitude of men who undertake the defence of a position in argument.
In the confidence that the principles are true they are ready to
accept any consequence of their application. As though some principles
did not require to be judged from their results, and particularly from