regarding the immediate objects of our senses as not existing
independently of us was Bishop Berkeley (1685-1753). His _Three
Dialogues between Hylas and Philonous, in Opposition to Sceptics and
Atheists_, undertake to prove that there is no such thing as matter at
all, and that the world consists of nothing but minds and their ideas.
Hylas has hitherto believed in matter, but he is no match for
Philonous, who mercilessly drives him into contradictions and
paradoxes, and makes his own denial of matter seem, in the end, as if
it were almost common sense. The arguments employed are of very
different value: some are important and sound, others are confused or
quibbling. But Berkeley retains the merit of having shown that the
existence of matter is capable of being denied without absurdity, and
that if there are any things that exist independently of us they
cannot be the immediate objects of our sensations.

There are two different questions involved when we ask whether matter
exists, and it is important to keep them clear. We commonly mean by
'matter' something which is opposed to 'mind', something which we
think of as occupying space and as radically incapable of any sort of
thought or consciousness. It is chiefly in this sense that Berkeley
denies matter; that is to say, he does not deny that the sense-data
which we commonly take as signs of the existence of the table are
really signs of the existence of _something_ independent of us, but he
does deny that this something is non-mental, that it is neither mind
nor ideas entertained by some mind. He admits that there must be
something which continues to exist when we go out of the room or shut
our eyes, and that what we call seeing the table does really give us
reason for believing in something which persists even when we are not
seeing it. But he thinks that this something cannot be radically
different in nature from what we see, and cannot be independent of