ruth about them. Knowledge of things by _description_, on the
contrary, always involves, as we shall find in the course of the present
chapter, some knowledge of truths as its source and ground. But first of
all we must make clear what we mean by 'acquaintance' and what we mean
by 'description'.

We shall say that we have _acquaintance_ with anything of which we are
directly aware, without the intermediary of any process of inference
or any knowledge of truths. Thus in the presence of my table I am
acquainted with the sense-data that make up the appearance of my
table--its colour, shape, hardness, smoothness, etc.; all these are
things of which I am immediately conscious when I am seeing and touching
my table. The particular shade of colour that I am seeing may have many
things said about it--I may say that it is brown, that it is rather
dark, and so on. But such statements, though they make me know truths
about the colour, do not make me know the colour itself any better
than I did before so far as concerns knowledge of the colour itself, as
opposed to knowledge of truths about it, I know the colour perfectly and
completely when I see it, and no further knowledge of it itself is even
theoretically possible. Thus the sense-data which make up the
appearance of my table are things with which I have acquaintance, things
immediately known to me just as they are.

My knowledge of the table as a physical object, on the contrary, is not
direct knowledge. Such as it is, it is obtained through acquaintance
with the sense-data that make up the appearance of the table. We have
seen that it is possible, without absurdity, to doubt whether there is
a table at all, whereas it is not possible to doubt the sense-data. My
knowledge of the table is of the kind which we shall call 'knowledge
by description'. The table is 'the physical object which causes
such-and-such sense-data'. This describes the table by means of the
sense-data. In order to know anything at all about the table, we must
know truths connecting it with things with which we have acquaintance:
we must know that 'such-and-such sense-data are caused by a physical
object'. There is no state of mind in which we are directly aware of the
table; all our knowledge of the table is really knowledge of truths, and
the actual thing which is the table is not, strictly speaking, known
to us at all. We know a description, and we know that there is just one
object to which this descript