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Full Online Book HomeEssaysProblems Of Philosophy - Chapter V - KNOWLEDGE BY ACQUAINTANCE AND KNOWLEDGE BY DESCRIPTION
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Problems Of Philosophy - Chapter V - KNOWLEDGE BY ACQUAINTANCE AND KNOWLEDGE BY DESCRIPTION Post by :Michelle1969 Category :Essays Author :Bertrand Russell Date :May 2011 Read :3578

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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 truth 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

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
thc 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
description applies, though the object itself is not directly known to
us. In such a case, we say that our knowledge of the object is
knowledge by description.

All our knowledge, both knowledge of things and knowledge of truths,
rests upon acquaintance as its foundation. It is therefore important
to consider what kinds of things there are with which we have

Sense-data, as we have already seen, are among the things with which
we are acquainted; in fact, they supply the most obvious and striking
example of knowledge by acquaintance. But if they were the sole
example, our knowledge would be very much more restricted than it is.
We should only know what is now present to our senses: we could not
know anything about the past--not even that there was a past--nor
could we know any truths about our sense-data, for all knowledge of
truths, as we shall show, demands acquaintance with things which are
of an essentially different character from sense-data, the things
which are sometimes called 'abstract ideas', but which we shall call
'universals'. We have therefore to consider acquaintance with other
things besides sense-data if we are to obtain any tolerably adequate
analysis of our knowledge.

The first extension beyond sense-data to be considered is acquaintance
by _memory_. It is obvious that we often remember what we have seen
or heard or had otherwise present to our senses, and that in such
cases we are still immediately aware of what we remember, in spite of
the fact that it appears as past and not as present. This immediate
knowledge by memory is the source of all our knowledge concerning the
past: without it, there could be no knowledge of the past by
inference, since we should never know that there was anything past to
be inferred.

The next extension to be considered is acquaintance by
_introspection_. We are not only aware of things, but we are often
aware of being aware of them. When I see the sun, I am often aware of
my seeing the sun; thus 'my seeing the sun' is an object with which I
have acquaintance. When I desire food, I may be aware of my desire
for food; thus 'my desiring food' is an object with which I am
acquainted. Similarly we may be aware of our feeling pleasure or
pain, and generally of the events which happen in our minds. This
kind of acquaintance, which may be called self-consciousness, is the
source of all our knowledge of mental things. It is obvious that it
is only what goes on in our own minds that can be thus known
immediately. What goes on in the minds of others is known to us
through our perception of their bodies, that is, through the
sense-data in us which are associated with their bodies. But for our
acquaintance with the contents of our own minds, we should be unable
to imagine the minds of others, and therefore we could never arrive at
the knowledge that they have minds. It seems natural to suppose that
self-consciousness is one of the things that distinguish men from
animals: animals, we may suppose, though they have acquaintance with
sense-data, never become aware of this acquaintance. I do not mean
that they _doubt whether they exist, but that they have never become
conscious of the fact that they have sensations and feelings, nor
therefore of the fact that they, the subjects of their sensations and
feelings, exist.

We have spoken of acquaintance with the contents of our minds as
_self_-consciousness, but it is not, of course, consciousness of our
_self_: it is consciousness of particular thoughts and feelings. The
question whether we are also acquainted with our bare selves, as
opposed to particular thoughts and feelings, is a very difficult one,
upon which it would be rash to speak positively. When we try to look
into ourselves we always seem to come upon some particular thought or
feeling, and not upon the 'I' which has the thought or feeling.
Nevertheless there are some reasons for thinking that we are
acquainted with the 'I', though the acquaintance is hard to
disentangle from other things. To make clear what sort of reason
there is, let us consider for a moment what our acquaintance with
particular thoughts really involves.

When I am acquainted with 'my seeing the sun', it seems plain that I
am acquainted with two different things in relation to each other. On
the one hand there is the sense-datum which represents the sun to me,
on the other hand there is that which sees this sense-datum. All
acquaintance, such as my acquaintance with the sense-datum which
represents the sun, seems obviously a relation between the person
acquainted and the object with which the person is acquainted. When a
case of acquaintance is one with which I can be acquainted (as I am
acquainted with my acquaintance with the sense-datum representing the
sun), it is plain that the person acquainted is myself. Thus, when I
am acquainted with my seeing the sun, the whole fact with which I am
acquainted is 'Self-acquainted-with-sense-datum'.

Further, we know the truth 'I am acquainted with this sense-datum'.
It is hard to see how we could know this truth, or even understand
what is meant by it, unless we were acquainted with something which we
call 'I'. It does not seem necessary to suppose that we are
acquainted with a more or less permanent person, the same to-day as
yesterday, but it does seem as though we must be acquainted with that
thing, whatever its nature, which sees the sun and has acquaintance
with sense-data. Thus, in some sense it would seem we must be
acquainted with our Selves as opposed to our particular experiences.
But the question is difficult, and complicated arguments can be
adduced on either side. Hence, although acquaintance with ourselves
seems _probably to occur, it is not wise to assert that it
undoubtedly does occur.

We may therefore sum up as follows what has been said concerning
acquaintance with things that exist. We have acquaintance in
sensation with the data of the outer senses, and in introspection with
the data of what may be called the inner sense--thoughts, feelings,
desires, etc.; we have acquaintance in memory with things which have
been data either of the outer senses or of the inner sense. Further,
it is probable, though not certain, that we have acquaintance with
Self, as that which is aware of things or has desires towards things.

In addition to our acquaintance with particular existing things, we
also have acquaintance with what we shall call _universals_, that is
to say, general ideas, such as _whiteness_, _diversity_,
_brotherhood_, and so on. Every complete sentence must contain at
least one word which stands for a universal, since all verbs have a
meaning which is universal. We shall return to universals later on,
in Chapter IX; for the present, it is only necessary to guard against
the supposition that whatever we can be acquainted with must be
something particular and existent. Awareness of universals is called
_conceiving_, and a universal of which we are aware is called a

It will be seen that among the objects with which we are acquainted
are not included physical objects (as opposed to sense-data), nor
other people's minds. These things are known to us by what I call
'knowledge by description', which we must now consider.

By a 'description' I mean any phrase of the form 'a so-and-so' or 'the
so-and-so'. A phrase of the form 'a so-and-so' I shall call an
'ambiguous' description; a phrase of the form 'the so-and-so' (in the
singular) I shall call a 'definite' description. Thus 'a man' is an
ambiguous description, and 'the man with the iron mask' is a definite
description. There are various problems connected with ambiguous
descriptions, but I pass them by, since they do not directly concern
the matter we are discussing, which is the nature of our knowledge
concerning objects in cases where we know that there is an object
answering to a definite description, though we are not acquainted with
any such object. This is a matter which is concerned exclusively with
definite descriptions. I shall therefore, in the sequel, speak simply
of 'descriptions' when I mean 'definite descriptions'. Thus a
description will mean any phrase of the form 'the so-and-so' in the

We shall say that an object is 'known by description' when we know
that it is 'the so-and-so', i.e. when we know that there is one
object, and no more, having a certain property; and it will generally
be implied that we do not have knowledge of the same object by
acquaintance. We know that the man with the iron mask existed, and
many propositions are known about him; but we do not know who he was.
We know that the candidate who gets the most votes will be elected,
and in this case we are very likely also acquainted (in the only sense
in which one can be acquainted with some one else) with the man who
is, in fact, the candidate who will get most votes; but we do not know
which of the candidates he is, i.e. we do not know any proposition of
the form 'A is the candidate who will get most votes' where A is one
of the candidates by name. We shall say that we have 'merely
descriptive knowledge' of the so-and-so when, although we know that
the so-and-so exists, and although we may possibly be acquainted with
the object which is, in fact, the so-and-so, yet we do not know any
proposition '_a is the so-and-so', where _a is something with which
we are acquainted.

When we say 'the so-and-so exists', we mean that there is just one
object which is the so-and-so. The proposition '_a is the so-and-so'
means that _a has the property so-and-so, and nothing else has. 'Mr.
A. is the Unionist candidate for this constituency' means 'Mr. A.
is a Unionist candidate for this constituency, and no one else is'.
'The Unionist candidate for this constituency exists' means 'some one
is a Unionist candidate for this constituency, and no one else is'.
Thus, when we are acquainted with an object which is the so-and-so, we
know that the so-and-so exists; but we may know that the so-and-so
exists when we are not acquainted with any object which we know to be
the so-and-so, and even when we are not acquainted with any object
which, in fact, is the so-and-so.

Common words, even proper names, are usually really descriptions.
That is to say, the thought in the mind of a person using a proper
name correctly can generally only be expressed explicitly if we
replace the proper name by a description. Moreover, the description
required to express the thought will vary for different people, or for
the same person at different times. The only thing constant (so long
as the name is rightly used) is the object to which the name applies.
But so long as this remains constant, the particular description
involved usually makes no difference to the truth or falsehood of the
proposition in which the name appears.

Let us take some illustrations. Suppose some statement made about
Bismarck. Assuming that there is such a thing as direct acquaintance
with oneself, Bismarck himself might have used his name directly to
designate the particular person with whom he was acquainted. In this
case, if he made a judgement about himself, he himself might be a
constituent of the judgement. Here the proper name has the direct use
which it always wishes to have, as simply standing for a certain
object, and not for a description of the object. But if a person who
knew Bismarck made a judgement about him, the case is different. What
this person was acquainted with were certain sense-data which he
connected (rightly, we will suppose) with Bismarck's body. His body,
as a physical object, and still more his mind, were only known as the
body and the mind connected with these sense-data. That is, they were
known by description. It is, of course, very much a matter af chance
which characteristics of a man's appearance will come into a friend's
mind when he thinks of him; thus the description actually in the
friend's mind is accidental. The essential point is that he knows
that the various descriptions all apply to the same entity, in spite
of not being acquainted with the entity in question.

When we, who did not know Bismarck, make a judgement about him, the
description in our minds will probably be some more or less vague mass
of historical knowledge--far more, in most cases, than is required to
identify him. But, for the sake of illustration, let us assume that
we think of him as 'the first Chancellor of the German Empire'. Here
all the words are abstract except 'German'. The word 'German' will,
again, have different meanings for different people. To some it will
recall travels in Germany, to some the look of Germany on the map, and
so on. But if we are to obtain a description which we know to be
applicable, we shall be compelled, at some point, to bring in a
reference to a particular with which we are acquainted. Such
reference is involved in any mention of past, present, and future (as
opposed to definite dates), or of here and there, or of what others
have told us. Thus it would seem that, in some way or other, a
description known to be applicable to a particular must involve some
reference to a particular with which we are acquainted, if our
knowledge about the thing described is not to be merely what follows
_logically from the description. For example, 'the most long-lived
of men' is a description involving only universals, which must apply
to some man, but we can make no judgements concerning this man which
involve knowledge about him beyond what the description gives. If,
however, we say, 'The first Chancellor of the German Empire was an
astute diplomatist', we can only be assured of the truth of our
judgement in virtue of something with which we are acquainted--usually
a testimony heard or read. Apart from the information we convey to
others, apart from the fact about the actual Bismarck, which gives
importance to our judgement, the thought we really have contains the
one or more particulars involved, and otherwise consists wholly of

All names of places--London, England, Europe, the Earth, the Solar
System--similarly involve, when used, descriptions which start from
some one or more particulars with which we are acquainted. I suspect
that even the Universe, as considered by metaphysics, involves such a
connexion with particulars. In logic, on the contrary, where we are
concerned not merely with what does exist, but with whatever might or
could exist or be, no reference to actual particulars is involved.

It would seem that, when we make a statement about something only
known by description, we often _intend to make our statement, not in
the form involving the description, but about the actual thing
described. That is to say, when we say anything about Bismarck, we
should like, if we could, to make the judgement which Bismarck alone
can make, namely, the judgement of which he himself is a constituent.
In this we are necessarily defeated, since the actual Bismarck is
unknown to us. But we know that there is an object B, called
Bismarck, and that B was an astute diplomatist. We can thus
_describe the proposition we should like to affirm, namely, 'B was an
astute diplomatist', where B is the object which was Bismarck. If we
are describing Bismarck as 'the first Chancellor of the German
Empire', the proposition we should like to affirm may be described as
'the proposition asserting, concerning the actual object which was the
first Chancellor of the German Empire, that this object was an astute
diplomatist'. What enables us to communicate in spite of the varying
descriptions we employ is that we know there is a true proposition
concerning the actual Bismarck, and that however we may vary the
description (so long as the description is correct) the proposition
described is still the same. This proposition, which is described and
is known to be true, is what interests us; but we are not acquainted
with the proposition itself, and do not know it, though we know it is

It will be seen that there are various stages in the removal from
acquaintance with particulars: there is Bismarck to people who knew
him; Bismarck to those who only know of him through history; the man
with the iron mask; the longest-lived of men. These are progressively
further removed from acquaintance with particulars; the first comes as
near to acquaintance as is possible in regard to another person; in
the second, we shall still be said to know 'who Bismarck was'; in the
third, we do not know who was the man with the iron mask, though we
can know many propositions about him which are not logically deducible
from the fact that he wore an iron mask; in the fourth, finally, we
know nothing beyond what is logically deducible from the definition of
the man. There is a similar hierarchy in the region of universals.
Many universals, like many particulars, are only known to us by
description. But here, as in the case of particulars, knowledge
concerning what is known by description is ultimately reducible to
knowledge concerning what is known by acquaintance.

The fundamental principle in the analysis of propositions containing
descriptions is this: _Every proposition which we can understand must
be composed wholly of constituents with which we are acquainted_.

We shall not at this stage attempt to answer all the objections which
may be urged against this fundamental principle. For the present, we
shall merely point out that, in some way or other, it must be possible
to meet these objections, for it is scarcely conceivable that we can
make a judgement or entertain a supposition without knowing what it is
that we are judging or supposing about. We must attach _some meaning
to the words we use, if we are to speak significantly and not utter
mere noise; and the meaning we attach to our words must be something
with which we are acquainted. Thus when, for example, we make a
statement about Julius Caesar, it is plain that Julius Caesar himself
is not before our minds, since we are not acquainted with him. We
have in mind some description of Julius Caesar: 'the man who was
assassinated on the Ides of March', 'the founder of the Roman Empire',
or, perhaps, merely 'the man whose name was _Julius Caesar_'. (In
this last description, _Julius Caesar is a noise or shape with which
we are acquainted.) Thus our statement does not mean quite what it
seems to mean, but means something involving, instead of Julius
Caesar, some description of him which is composed wholly of
particulars and universals with which we are acquainted.

The chief importance of knowledge by description is that it enables us
to pass beyond the limits of our private experience. In spite of the
fact that we can only know truths which are wholly composed of terms
which we have experienced in acquaintance, we can yet have knowledge
by description of things which we have never experienced. In view of
the very narrow range of our immediate experience, this result is
vital, and until it is understood, much of our knowledge must remain
mysterious and therefore doubtful.


(Bertrand Russell's essay: The Problems of Philosophy)

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