knowledge, in which, though the _possibility_ of error remains, its
likelihood is diminished by the interrelation of the parts and by the
critical scrutiny which has preceded acquiescence.

This function, at least, philosophy can perform. Most philosophers,
rightly or wrongly, believe that philosophy can do much more than
this--that it can give us knowledge, not otherwise attainable,
concerning the universe as a whole, and concerning the nature of
ultimate reality. Whether this be the case or not, the more modest
function we have spoken of can certainly be performed by philosophy,
and certainly suffices, for those who have once begun to doubt the
adequacy of common sense, to justify the arduous and difficult labours
that philosophical problems involve.


CHAPTER III
THE NATURE OF MATTER

In the preceding chapter we agreed, though without being able to find
demonstrative reasons, that it is rational to believe that our
sense-data--for example, those which we regard as associated with my
table--are really signs of the existence of something independent of
us and our perceptions. That is to say, over and above the sensations
of colour, hardness, noise, and so on, which make up the appearance of
the table to me, I assume that there is something else, of which these
things are appearances. The colour ceases to exist if I shut my eyes,
the sensation of hardness ceases to exist if I remove my arm from
contact with the table, the sound ceases to exist if I cease to rap
the table with my knuckles. But I do not believe that when all these
things cease the table ceases. On the contrary, I believe that it is