possible but necessary to distinguish what a thing
looks from what it is, and precisely in consequence of the nature of
space. The visual perception of spatial relations from its very nature
presupposes a particular point of view. Though the perception itself
cannot be spatial, it presupposes a particular point in space as a
standpoint or point of view,[18] and is therefore subject to
conditions of perspective. This is best realized by considering the
supposition that perfect visual powers would enable us to see the
whole of a body at once, and that this perception would be possible if
we had eyes situated all round the body. The supposition obviously
breaks down through the impossibility of combining two or more points
of view in one perception. But if visual perception is necessarily
subject to conditions of perspective, the spatial relations of bodies
can never look what they are except in the limiting case referred to.
Moreover, this distinction is perfectly intelligible, as we should
expect from the necessity which we are under of drawing it. We
understand perfectly why it is that bodies must, in respect of their
spatial relations, look different to what they are, and we do so
solely because we understand the nature of space, and therefore also
the conditions of perspective involved in the perception of what is
spatial. It is, therefore, needless to make the assertion 'Two lines
appear convergent' intelligible by converting the verb 'appears' into
a substantive, viz. an 'appearance', and then making the assertion
relate to an 'appearance'. For--apart from the fact that this would
not achieve the desired end, since no suitable predicate could be
found for the appearance--the assertion that the lines _look_ or
_appear_ convergent is perfectly intelligible in itself, though not
capable of being stated in terms of anything else.[19] If we
generalize this result, we may say that the distinction between
appearance and reality, drawn with regard to the primary qualities of
bodies, throughout presupposes the reality of space, and is made
possible, and indeed necessary, by the nature of space itself.

[17] Cf., however, p. 87 and pp. 89-91.

[18] This is, of course, not refuted by the reminder that we
see with two eyes, and that these are in different places.

[19] It is important to notice that the proper formula to
express what is loosely called 'an appearance' is 'A looks or
appears B', and th