On Sense And The Sensible
that the Pythagoreans named the superficies of a body its 'hue', for
'hue', indeed, lies at the limit of the body; but the limit of the
body; is not a real thing; rather we must suppose that the same
natural substance which, externally, is the vehicle of colour exists
[as such a possible vehicle] also in the interior of the body.
Air and water, too [i.e. as well as determinately bounded bodies]
are seen to possess colour; for their brightness is of the nature of
colour. But the colour which air or sea presents, since the body in
which it resides is not determinately bounded, is not the same when
one approaches and views it close by as it is when one regards it from
a distance; whereas in determinate bodies the colour presented is
definitely fixed, unless, indeed, when the atmospheric environment
causes it to change. Hence it is clear that that in them which is
susceptible of colour is in both cases the same. It is therefore the
Translucent, according to the degree to which it subsists in bodies
(and it does so in all more or less), that causes them to partake of
colour. But since the colour is at the extremity of the body, it
must be at the extremity of the Translucent in the body. Whence it
follows that we may define colour as the limit of the Translucent in
determinately bounded body. For whether we consider the special
class of bodies called translucent, as water and such others, or
determinate bodies, which appear to possess a fixed colour of their
own, it is at the exterior bounding surface that all alike exhibit
Now, that which when present in air produces light may be present
also in the Translucent which pervades determinate bodies; or again,
it may not be present, but there may be a privation of it.
Accordingly, as in the case of air the one condition is light, the
other darkness, in the same way the colours White and Black are
generated in determinate bodies.
We must now treat of the other colours, reviewing the several
hypotheses invented to explain their genesis.