 The
Problems of Philosophy
Bertrand Russell
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 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 dear 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 a 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 whet 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 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 acquaintance.
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 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, 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 concept.
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
singular.
We 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 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 of 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 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. or 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 concepts.
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 diplomat', 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 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 be 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 true.
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, 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 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.
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