ities. They
imply that what we perceive is a reality, in the sense already
explained.[25] Thus the assertion that the grass looks green implies
that it is a reality which looks green, or, in other words, that the
object of perception is a reality, and not an 'appearance'. Again,
such assertions imply that the reality about which the assertion is
made is spatial. The term 'grass' implies extension, and only what is
extended can be said to look coloured. If it be urged that what looks
coloured need only _look_ extended, it may be replied that the two
considerations which lead us to think that things only _look_ coloured
presuppose that they _are_ spatial. For the two questions, the
consideration of which leads to this conclusion, are, 'What is the
right or real colour of an individual thing?' and 'Has it really any
colour at all, or does it only look coloured?' and neither question is
significant unless the thing to which it refers is understood to be
spatial.

[25] I. e. in the sense of something which exists
independently of perception.

We may now return to the main issue. Is it possible to maintain either
(1) the position that only appearances are spatial and possess all the
qualities which imply space, or (2) the position that things only
appear spatial and only appear or look as if they possessed the
qualities which imply space? It may be urged that these questions have
already been implicitly answered in the negative. For the division of
the qualities of things into primary and secondary is exhaustive, and,
as has been shown, the distinction between 'appearance' and 'reality',
when drawn with respect to the primary qualities and to colour--the
only secondary quality with respect to which the term 'appears' can
properly be used[26]--presupposes the reality of space. Consequently,
since we do draw the distinction, we must accept the reality of that
which is the condition of drawing it at all. But even though this be
conceded--and the concession is inevitable--the problem cannot be
regarded as solved until we have discovered what it is in the nature
of space which makes both positions untenable. Moreover, the admission
that in the case of colour there is no identity between what things
look and what they are removes at a stroke much of the difficulty of
one position, viz. that we only know what things look or appear, and
not what they are. For the admission makes it impossible to maintain
as a general princ