In general the sensation of sight consists of perception of the visible
object, and by sight we attain it in the place where the object is
placed before our eyes, as if the perception operated in that very
place, and as if the soul saw outside of herself. This occurs, I
think, without any image being produced nor producing itself outside
of the soul, without the soul receiving any impression similar to that
imparted by the seal to the wax. Indeed, if the soul already in herself
possessed the image of the visible object, the mere possession of this
image (or type) would free her from the necessity of looking outside
of herself. The calculation of the distance of the object's location,
and visibility proves that the soul does not within herself contain
the image of the object. In this case, as the object would not be
distant from her, the soul would not see it as located at a distance.
Besides, from the image she would receive from within herself, the soul
could not judge of the size of the object, or even determine whether
it possessed any magnitude at all. For instance, taking as an example
the sky, the image which the soul would develop of it would not be
so great (as it is, when the soul is surprised at the sky's extent).
Besides, there is a further objection, which is the most important of
all. If we perceive only the images of the objects we see, instead of
seeing the objects themselves, we would see only their appearances or
adumbrations. Then the realities would differ from the things that we
see. The true observation that we cannot discern an object placed upon
the pupil, though we can see it at some little distance, applies with
greater cogency to the soul. If the image of the visible object be
located within her, she will not see the object that yields her this
image. We have to distinguish two things, the object seen, and the
seeing subject; consequently, the subject that sees the visible object
must be distinct from it, and see it as located elsewhere than within
itself. The primary condition of the act of vision therefore is, not
that the image of the object be located in the soul, but that it be
located outside of the soul.