mentioned as the immediate objects of sight are not visible but tangible
planes. For when we say that pictures are planes, we mean thereby that
they appear to the touch smooth and uniform. But then this smoothness and
uniformity, or, in other words, this planeness of the picture, is not
perceived immediately by vision: for it appeareth to the eye various and
multiform.

158. From all which we may conclude that planes are no more the immediate
object of sight than solids. What we strictly see are not solids, nor yet
planes variously coloured: they are only diversity of colours. And some
of these suggest to the mind solids, and other plane figures, just as
they have been experienced to be connected with the one or the other: so
that we see planes in the same way that we see solids, both being equally
suggested by the immediate objects of sight, which accordingly are
themselves denominated planes and solids. But though they are called by
the same names with the things marked by them, they are nevertheless of a
nature entirely different, as hath been demonstrated.

159. What hath been said is, if I mistake not, sufficient to decide the
question we proposed to examine, concerning the ability of a pure spirit,
such as we have described, to know GEOMETRY. It is, indeed, no easy
matter for us to enter precisely into the thoughts of such an
intelligence, because we cannot without great pains cleverly separate and
disentangle in our thoughts the proper objects of sight from those of
touch which are connected with them. This, indeed, in a complete degree
seems scarce possible to be performed: which will not seem strange to us
if we consider how hard it is for anyone to hear the words of his native
language pronounced in his ears without understanding them. Though he
endeavour to disunite the meaning from the sound, it will nevertheless
intrude into his thoughts, and he shall find it extreme difficult, if not