'But, say you, surely there is nothing easier than for me to imagine
trees, for instance, in a park, or books existing in a closet, and
nobody by to perceive them. I answer, you may so, there is no
difficulty in it; but what is all this, I beseech you, more than
framing in your mind certain ideas which you call books and trees, and
{15} at the same time omitting to frame the idea of any one that may
perceive them? But do not you yourself perceive or think of them all
the while? This therefore is nothing to the purpose: it only shews you
have the power of imagining or forming ideas in your mind; but it does
not shew that you can conceive it possible the objects of your thought
may exist without the mind. To make out this, it is necessary that
_you_ conceive them existing unconceived or unthought of, which is a
manifest repugnancy. When we do our utmost to conceive the existence
of external bodies, we are all the while only contemplating our own
ideas. But the mind, _taking no notice of itself_, is deluded to think
it can and does conceive bodies existing unthought of or without the
mind, though at the same time they are apprehended by, or exist in,
itself. A little attention will discover to any one the truth and
evidence of what is here said, and make it unnecessary to insist on any
other proofs against the existence of _material substance_.'[5]

Berkeley no doubt did not adequately appreciate the importance of the
distinction between mere sensations and mental relations. In the
paragraph which I have read to you he tends to explain space away into
mere subjective feelings: in this respect and in many others he has
been corrected by Kant and the post-Kantian Idealists. Doubtless we
cannot analyse away our conception of space or of substance into mere
feelings. But relations imply mind no less than sensations. Things
are no mere {16} bundles of sensations; we do think of them as objects
or substances possessing attributes. Indeed to call them (with
Berkeley), 'bundles of sensations' implies that the bundle is as
important an element in thinghood as the sensations themselves. The
bundle implies what Kant would call the intellectual 'categories' of
Substance, Quantity, Quality, and the like. We do think objects: but
an object is still an object of thought. We can attach no intelligible
meaning to the term 'object' which does not imply a subject.

If there is nothing in matter, as we know it, which doe