In
order then that it might not tumble about among the high and deep
places of the earth, but might be able to get over the one and
out of the other, they provided the body to be its vehicle and
means of locomotion; which consequently had length and was
furnished with four limbs extended and flexible; these God
contrived to be instruments of locomotion with which it might
take hold and find support, and so be able to pass through all
places, carrying on high the dwelling-place of the most sacred
and divine part of us. Such was the origin of legs and hands,
which for this reason were attached to every man; and the gods,
deeming the front part of man to be more honourable and more fit
to command than the hinder part, made us to move mostly in a
forward direction. Wherefore man must needs have his front part
unlike and distinguished from the rest of his body.
And so in the vessel of the head, they first of all put a face
in which they inserted organs to minister in all things to the
providence of the soul, and they appointed this part, which has
authority, to be by nature the part which is in front. And of the
organs they first contrived the eyes to give light, and the
principle according to which they were inserted was as follows:
So much of fire as would not burn, but gave a gentle light, they
formed into a substance akin to the light of every-day life; and
the pure fire which is within us and related thereto they made to
flow through the eyes in a stream smooth and dense, compressing
the whole eye, and especially the centre part, so that it kept
out everything of a coarser nature, and allowed to pass only this
pure element. When the light of day surrounds the stream of
vision, then like falls upon like, and they coalesce, and one
body is formed by natural affinity in the line of vision,
wherever the light that falls from within meets with an external
object. And the whole stream of vision, being similarly affected
in virtue of similarity, diffuses the motions of what it touches
or what touches it over the whole body, until they reach the
soul, causing that perception which we call sight. But when night
comes on and the external and kindred fire departs, then the
stream of vision is cut off; for going forth to an unlike element
it is changed and extinguished, being no longer of one nature
with the surrounding atmosphere which is now deprived of fire:
and so the eye no longer sees, and we feel disposed to sleep. For
when the eyelids, which the gods invented for the preservation of
sight, are closed, they keep in the internal fire; and the power
of the fire diffuses and equalises the inward motions; when they
are equalised, there is rest, and when the rest is profound,
sleep comes over us scarce disturbed by dreams; but where the
greater motions still remain, of whatever nature and in whatever
locality, they engender corresponding visions in dreams, which
are remembered by us when we are awake and in the external world.
And now there is no longer any difficulty in understanding the
creation of images in mirrors and all smooth and bright surfaces.
For from the communion of the internal and external fires, and
again from the union of them and their numerous transformations
when they meet in the mirror, all these appearances of necessity
arise, when the fire from the face coalesces with the fire from
the eye on the bright and smooth surface. And right appears left
and left right, because the visual rays come into contact with
the rays emitted by the object in a manner contrary to the usual
mode of meeting; but the right appears right, and the left left,
when the position of one of the two concurring lights is
reversed; and this happens when the mirror is concave and its
smooth surface repels the right stream of vision to the left
side, and the left to the right. Or if the mirror be turned
vertically, then the concavity makes the countenance appear to be
all upside down, and the lower rays are driven upwards and the
upper downwards.
All these are to be reckoned among the second and co-operative
causes which God, carrying into execution the idea of the best as
far as possible, uses as his ministers. They are thought by most
men not to be the second, but the prime causes of all things,
because they freeze and heat, and contract and dilate, and the
like. But they are not so, for they are incapable of reason or
intellect; the only being which can properly have mind is the
invisible soul, whereas fire and water, and earth and air, are
all of them visible bodies. The lover of intellect and knowledge
ought to explore causes of intelligent nature first of all, and,
secondly, of those things which, being moved by others, are
compelled to move others.
