tever 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
(He is speaking of two kinds of mirrors, first the plane, secondly the
concave; and the latter is supposed to be placed, first horizontally,
and then vertically.). 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. And this is what we too must do. Both kinds
of causes should be acknowledged by us, but a distinction should be made
between those which are endowed with mind and are the workers of things
fair and good, and those which are deprived of intelligence and always
produce chance effects without order or design. Of the second or
co-operative causes of sight, which help to give to the eyes the power
which they now po