know sense-data.
(The distinction involved is roughly that between _savoir_ and
_connaitre_ in French, or between _wissen_ and _kennen_ in German.)

Thus the statement which seemed like a truism becomes, when re-stated,
the following: 'We can never truly judge that something with which we
are not acquainted exists.' This is by no means a truism, but on the
contrary a palpable falsehood. I have not the honour to be acquainted
with the Emperor of China, but I truly judge that he exists. It may
be said, of course, that I judge this because of other people's
acquaintance with him. This, however, would be an irrelevant retort,
since, if the principle were true, I could not know that any one else
is acquainted with him. But further: there is no reason why I should not
know of the existence of something with which nobody is acquainted. This
point is important, and demands elucidation.

If I am acquainted with a thing which exists, my acquaintance gives
me the knowledge that it exists. But it is not true that, conversely,
whenever I can know that a thing of a certain sort exists, I or some one
else must be acquainted with the thing. What happens, in cases where I
have true judgement without acquaintance, is that the thing is known to
me by _description_, and that, in virtue of some general principle, the
existence of a thing answering to this description can be inferred
from the existence of something with which I am acquainted. In order
to understand this point fully, it will be well first to deal with
the difference between knowledge by acquaintance and knowledge by
description, and then to consider what knowledge of general principles,
if any, has the same kind of certainty as our knowledge of the existence
of our own experiences. These subjects will be dealt with in the
following chapters.

CHAPTER V. KNOWLEDGE BY ACQUAINTANCE AND KNOWLEDGE BY DESCRIPTION

In the preceding chapter we saw that there are two sorts of knowledge:
knowledge of things, and knowledge of truths. In this chapter we shall
be concerned exclusively with knowledge of things, of which in turn we
shall have to distinguish two kinds. Knowledge of things, when it is
of the kind we call knowledge by _acquaintance_, is essentially simpler
than any knowledge of truths, and logically independent of knowledge
of truths, though it would be rash to assume that human beings ever,
in fact, have acquaintance with things without at the same time knowing
some t