New Theory of Vision."

"It will be objected that we see things actually without, or
at a distance from us, and which consequently do not exist in
the mind; it being absurd that those things which are seen at
the distance of several miles, should be as near to us as our
own thoughts. In answer to this, I desire it may be considered
that in a dream we do oft perceive things as existing at a
great distance off, and yet, for all that, those things are
acknowledged to have their existence only in the mind.

"But for the fuller clearing of this point, it may be worth
while to consider how it is that we perceive distance and
things placed at a distance by sight. For that we should in
truth see external space and bodies actually existing in it,
some nearer, others further off, seems to carry with it some
opposition to what hath been said of their existing nowhere
without the mind. The consideration of this difficulty it
was that gave birth to my 'Essay towards the New Theory of
Vision,' which was published not long since, wherein it is
shown that distance, or outness, is neither immediately of
itself perceived by sight, nor yet apprehended, or judged
of, by lines and angles or anything that hath any necessary
connection with it; but that it is only suggested to our
thoughts by certain visible ideas and sensations attending
vision, which, in their own nature, have no manner of
similitude or relation either with distance, or with things
placed at a distance; but by a connection taught us by
experience, they come to signify and suggest them to us, after
the same manner that words of any language suggest the ideas