BOOK I PART IV
conceived to exist, by itself: but necessarily re-
quires some object or real existence, to which it
may belong. Now the difficulty still remains,
how to form an idea of this object or existence,
without having recourse to the secondary and
sensible qualities.
Nor must we omit on this occasion our ac-
customed method of examining ideas by con-
sidering those impressions, from which they
are derived. The impressions, which enter by
the sight and hearing, the smell and taste, are
affirmed by modern philosophy to be without
any resembling objects; and consequently the
idea of solidity, which is supposed to be real,
can never be derived from any of these senses.
There remains, therefore, the feeling as the only
sense, that can convey the impression, which
is original to the idea of solidity; and indeed