Afterwards, when upon turning his head or eyes up and down to the
right and left he shall observe the visible objects to change, and shall
also attain to know that they are called by the same names, and connected
with the objects perceived by touch; then indeed he will come to speak of
them and their situation, in the same terms that he has been used to
apply to tangible things; and those that he perceives by turning up his
eyes he will call upper, and those that by turning down his eyes he will
call lower.

98. And this seems to me the true reason why he should think those
objects uppermost that are painted on the lower part of his eye: for by
turning the eye up they shall be distinctly seen; as likewise those that
are painted on the highest part of the eye shall be distinctly seen by
turning the eye down, and are for that reason esteemed lowest; for we
have shown that to the immediate objects of sight considered in
themselves, he would not attribute the terms HIGH and LOW. It must
therefore be on account of some circumstances which are observed to
attend them: and these, it is plain, are the actions of turning the eye
up and down, which suggest a very obvious reason why the mind should
denominate the objects of sight accordingly high or low. And without this
motion of the eye, this turning it up and down in order to discern
different objects, doubtless ERECT, INVERSE, and other the like terms
relating to the position of tangible objects, would never have been
transferred, or in any degree apprehended to belong to the ideas of
sight: the mere act of seeing including nothing in it to that purpose;
whereas the different situations of the eye naturally direct the mind to
make a suitable judgment of the situation of objects intromitted by it.

99. Farther, when he has by experience learned the connexion there is
between the several ideas of sight and touch, he will be able, by the
perception he has of the situation of visible things in respect of one
another, to make a sudden and true estimate of the situation of outward,
tangible things corresponding to them. And thus it is he shall perceive
by sight the situation of external objects which do not properly fall
under that sense.

100. I know we are very prone to think that, if just made to see, we
should judge of the situation of visible things as we do now: but we are
also as prone to think that, at first sight, we should in the same way
apprehend the distance and magn