The Analysis of Mind, Bertrand Russell [best desktop ebook reader .txt] 📗

temperature.

 

Many difficult questions arise in connection with knowledge. It

is difficult to define knowledge, difficult to decide whether we

have any knowledge, and difficult, even if it is conceded that we

sometimes have knowledge to discover whether we can ever know

that we have knowledge in this or that particular case. I shall

divide the discussion into four parts:

 

I. We may regard knowledge, from a behaviourist standpoint, as

exhibited in a certain kind of response to the environment. This

response must have some characteristics which it shares with

those of scientific instruments, but must also have others that

are peculiar to knowledge. We shall find that this point of view

is important, but not exhaustive of the nature of knowledge.

 

II. We may hold that the beliefs that constitute knowledge are

distinguished from such as are erroneous or uncertain by

properties which are intrinsic either to single beliefs or to

systems of beliefs, being in either case discoverable without

reference to outside fact. Views of this kind have been widely

held among philosophers, but we shall find no reason to accept

them.

 

III. We believe that some beliefs are true, and some false. This

raises the problem of VERIFIABILITY: are there any circumstances

which can justifiably give us an unusual degree of certainty that

such and such a belief is true? It is obvious that there are

circumstances which in fact cause a certainty of this sort, and

we wish to learn what we can from examining these circumstances.

 

IV. Finally, there is the formal problem of defining truth and

falsehood, and deriving the objective reference of a proposition

from the meanings of its component words.

 

We will consider these four problems in succession.

 

I. We may regard a human being as an instrument, which makes

various responses to various stimuli. If we observe these

responses from outside, we shall regard them as showing knowledge

when they display two characteristics, ACCURACY and

APPROPRIATENESS. These two are quite distinct, and even sometimes

incompatible. If I am being pursued by a tiger, accuracy is

furthered by turning round to look at him, but appropriateness by

running away without making any search for further knowledge of

the beast. I shall return to the question of appropriateness

later; for the present it is accuracy that I wish to consider.

 

When we are viewing a man from the outside, it is not his

beliefs, but his bodily movements, that we can observe. His

knowledge must be inferred from his bodily movements, and

especially from what he says and writes. For the present we may

ignore beliefs, and regard a man’s knowledge as actually

consisting in what he says and does. That is to say, we will

construct, as far as possible, a purely behaviouristic account of

truth and falsehood.

 

If you ask a boy “What is twice two?” and the boy says “four,”

you take that as prima facie evidence that the boy knows what

twice two is. But if you go on to ask what is twice three, twice

four, twice five, and so on, and the boy always answers “four,”

you come to the conclusion that he knows nothing about it.

Exactly similar remarks apply to scientific instruments. I know a

certain weather-cock which has the pessimistic habit of always

pointing to the north-east. If you were to see it first on a cold

March day, you would think it an excellent weather-cock; but with

the first warm day of spring your confidence would be shaken. The

boy and the weather-cock have the same defect: they do not vary

their response when the stimulus is varied. A good instrument, or

a person with much knowledge, will give different responses to

stimuli which differ in relevant ways. This is the first point in

defining accuracy of response.

 

We will now assume another boy, who also, when you first question

him, asserts that twice two is four. But with this boy, instead

of asking him different questions, you make a practice of asking

him the same question every day at breakfast. You find that he

says five, or six, or seven, or any other number at random, and

you conclude that he also does not know what twice two is, though

by good luck he answered right the first time. This boy is like a

weather-cock which, instead of being stuck fast, is always going

round and round, changing without any change of wind. This boy

and weather-cock have the opposite defect to that of the previous

pair: they give different responses to stimuli which do not

differ in any relevant way.

 

In connection with vagueness in memory, we already had occasion

to consider the definition of accuracy. Omitting some of the

niceties of our previous discussion, we may say that an

instrument is ACCURATE when it avoids the defects of the two boys

and weather-cocks, that is to say, when—

 

(a) It gives different responses to stimuli which differ in

relevant ways;

 

(b) It gives the same response to stimuli which do not differ in

relevant ways.

 

What are relevant ways depends upon the nature and purpose of the

instrument. In the case of a weather-cock, the direction of the

wind is relevant, but not its strength; in the case of the boy,

the meaning of the words of your question is relevant, but not

the loudness of your voice, or whether you are his father or his

schoolmaster If, however, you were a boy of his own age, that

would be relevant, and the appropriate response would be

different.

 

It is clear that knowledge is displayed by accuracy of response

to certain kinds of stimuli, e.g. examinations. Can we say,

conversely, that it consists wholly of such accuracy of response?

I do not think we can; but we can go a certain distance in this

direction. For this purpose we must define more carefully the

kind of accuracy and the kind of response that may be expected

where there is knowledge.

 

From our present point of view, it is difficult to exclude

perception from knowledge; at any rate, knowledge is displayed by

actions based upon perception. A bird flying among trees avoids

bumping into their branches; its avoidance is a response to

visual sensations. This response has the characteristic of

accuracy, in the main, and leads us to say that the bird “knows,”

by sight, what objects are in its neighbourhood. For a

behaviourist, this must certainly count as knowledge, however it

may be viewed by analytic psychology. In this case, what is

known, roughly, is the stimulus; but in more advanced knowledge

the stimulus and what is known become different. For example, you

look in your calendar and find that Easter will be early next

year. Here the stimulus is the calendar, whereas the response

concerns the future. Even this can be paralleled among

instruments: the behaviour of the barometer has a present

stimulus but foretells the future, so that the barometer might be

said, in a sense, to know the future. However that may be, the

point I am emphasizing as regards knowledge is that what is known

may be quite different from the stimulus, and no part of the

cause of the knowledge-response. It is only in sense-knowledge

that the stimulus and what is known are, with qualifications,

identifiable. In knowledge of the future, it is obvious that they

are totally distinct, since otherwise the response would precede

the stimulus. In abstract knowledge also they are distinct, since

abstract facts have no date. In knowledge of the past there are

complications, which we must briefly examine.

 

Every form of memory will be, from our present point of view, in

one sense a delayed response. But this phrase does not quite

clearly express what is meant. If you light a fuse and connect it

with a heap of dynamite, the explosion of the dynamite may be

spoken of, in a sense, as a delayed response to your lighting of

the fuse. But that only means that it is a somewhat late portion

of a continuous process of which the earlier parts have less

emotional interest. This is not the case with habit. A display of

habit has two sorts of causes: (a) the past occurrences which

generated the habit, (b) the present occurrence which brings it

into play. When you drop a weight on your toe, and say what you

do say, the habit has been caused by imitation of your

undesirable associates, whereas it is brought into play by the

dropping of the weight. The great bulk of our knowledge is a

habit in this sense: whenever I am asked when I was born, I reply

correctly by mere habit. It would hardly be correct to say that

getting born was the stimulus, and that my reply is a delayed

response But in cases of memory this way of speaking would have

an element of truth. In an habitual memory, the event remembered

was clearly an essential part of the stimulus to the formation of

the habit. The present stimulus which brings the habit into play

produces a different response from that which it would produce if

the habit did not exist. Therefore the habit enters into the

causation of the response, and so do, at one remove, the causes

of the habit. It follows that an event remembered is an essential

part of the causes of our remembering.

 

In spite, however, of the fact that what is known is SOMETIMES an

indispensable part of the cause of the knowledge, this

circumstance is, I think, irrelevant to the general question with

which we are concerned, namely What sort of response to what sort

of stimulus can be regarded as displaying knowledge? There is one

characteristic which the response must have, namely, it must

consist of voluntary movements. The need of this characteristic

is connected with the characteristic of APPROPRIATENESS, which I

do not wish to consider as yet. For the present I wish only to

obtain a clearer idea of the sort of ACCURACY that a

knowledge-response must have. It is clear from many instances

that accuracy, in other cases, may be purely mechanical. The most

complete form of accuracy consists in giving correct answers to

questions, an achievement in which calculating machines far

surpass human beings. In asking a question of a calculating

machine, you must use its language: you must not address it in

English, any more than you would address an Englishman in

Chinese. But if you address it in the language it understands. it

will tell you what is 34521 times 19987, without a moment’s

hesitation or a hint of inaccuracy. We do not say the machine

KNOWS the answer, because it has no purpose of its own in giving

the answer: it does not wish to impress you with its cleverness,

or feel proud of being such a good machine. But as far as mere

accuracy goes, the machine leaves nothing to be desired.

 

Accuracy of response is a perfectly clear notion in the case of

answers to questions, but in other cases it is much more obscure.

We may say generally that an object whether animate or inanimate,

is “sensitive” to a certain feature of the environment if it

behaves differently according to the presence or absence of that

feature. Thus iron is sensitive to anything magnetic. But

sensitiveness does not constitute knowledge, and knowledge of a

fact which is not sensible is not sensitiveness to that fact, as

we have seen in distinguishing the fact known from the stimulus.

As soon as we pass beyond the simple case of question and answer,

the definition of knowledge by means of behaviour demands the

consideration of purpose. A carrier pigeon flies home, and so we

say it “knows” the way. But if it merely flew to some place at

random, we should not