In all this I have been considering the question of the relation

between the structure of language and the structure of the world. It is

clear that anything that can be said in an inflected language can be

said in an uninflected language; therefore, everything that can be said

in language can be said by means of a temporal series of uninflected

words. This places a limitation upon what can be expressed in words.

It may well be that there are facts which do not lend themselves to

this very simple schema; if so, they cannot be expressed in language.

Our confidence in language is due to the fact that it consists of

events in the physical world, and, therefore, shares the structure of

the physical world, and therefore can express that structure. But if

there be a world which is not physical, or not in space-time, it may

have a structure which we can never hope to express or to know. These

considerations might lead us to something like the Kantian _a priori_,

not as derived from the structure of the mind, but as derived from the

structure of language, which is the structure of the physical world.

Perhaps that is why we know so much physics and so little of anything

else. However, I have lapsed into mystical speculation, and will leave

these possibilities, since, by the nature of the case, I cannot _say_

anything true about them.

CHAPTER XXV

THE VALIDITY OF INFERENCE

It is customary in science to regard certain facts as “data”, from

which laws and also other facts are “inferred”. We saw in Chapter VII

that the _practice_ of inference is much wider than the theories of any

logician would justify, and that it is nothing other than the law of

association or of “learned reactions”. In the present chapter, I wish

to consider what the logicians have evolved from this primitive form of

inference, and what grounds we have, as rational beings, for continuing

to infer. But let us first get as clear a notion as we can of what

should be meant by a “datum”.

The conception of a “datum” cannot be made absolute. Theoretically,

it should mean something that we know without inference. But before

this has any definite meaning, we must define both “knowledge” and

“inference”. Both these terms have been considered in earlier chapters.

For our present purpose it will simplify matters to take account only

of such knowledge as is expressed in words. We considered in Chapter

XXIV the conditions required in order that a form of words may be

“true”; for present purposes, therefore, we may say that “knowledge”

means “the assertion of a true form of words”. This definition is not

quite adequate, since a man may be right by chance; but we may ignore

this complication. We may then define a “datum” as follows: A “datum”

is a form of words which a man utters as the result of a stimulus, with

no intermediary of any learned reaction beyond what is involved in

knowing how to speak. We must, however, permit such learned reactions

as consist in adjustments of the sense-organs or in mere increase of

sensitivity. These merely improve the receptivity to data, and do not

involve anything that can be called inference.

If the above definition is accepted, all our data for knowledge of

the external world must be of the nature of percepts. The belief in

external objects is a learned reaction acquired in the first months of

life, and it is the duty of the philosopher to treat it as an inference

whose validity must be tested. A very little consideration shows that,

logically, the inference cannot be demonstrative, but must be at best

probable. It is not logically _impossible_ that my life may be one

long dream, in which I merely imagine all the objects that I believe

to be external to me. If we are to reject this view, we must do so on

the basis of an inductive or analogical argument, which cannot give

complete certainty. We perceive other people behaving in a manner

analogous to that in which we behave, and we assume that they have had

similar stimuli. We may hear a whole crowd say “oh” at the moment when

we see a rocket burst, and it is natural to suppose that the crowd

saw it too. Nor are such arguments confined to living organisms. We

can talk to a dictaphone and have it afterwards repeat what we said;

this is most easily explained by the hypothesis that at the surface

of the dictaphone events happened, while I was speaking, which were

closely analogous to those that were happening just outside my ears.

It remains _possible_ that there is no dictaphone and I have no ears

and there is no crowd watching the rocket; my percepts _may_ be all

that is happening in such cases. But, if so, it is difficult to arrive

at any causal laws, and arguments from analogy are more misleading

than we are inclined to think them. As a matter of fact, the whole

structure of science, as well as the world of common sense, demands

the use of induction and analogy if it is to be believed. These forms

of inference, therefore, rather than deduction, are those that must be

examined if we are to accept the world of science or any world outside

of our own dreams.

Let us take a simple example of an induction which we have all

performed in practice. If we are hungry, we eat certain things we see

and not others--it may be said that we infer edibility inductively

from a certain visual and olfactory appearance. The history of this

process is that children a few months old put everything into their

mouths unless they are stopped; sometimes the result is pleasant,

sometimes unpleasant; they repeat the former rather than the latter.

That is to say: given that an object having a certain visual and

olfactory appearance has been found pleasant to eat, an object having

a very similar appearance will be eaten; but when a certain appearance

has been found connected with unpleasant consequences when eaten, a

similar appearance does not lead to eating next time. The question is:

what logical justification is there for our behaviour? Given all our

past experience, are we more likely to be nourished by bread than by a

stone? It is easy to see why we think so, but can we, as philosophers

justify this way of thinking?

It is, of course, obvious that unless one thing can be a sign of

another both science and daily life would be impossible. More

particularly, reading involves this principle. One accepts printed

words as signs, but this is only justifiable by means of induction.

I do not mean that induction is necessary to establish the existence

of other people, though that also, as we have seen, is true. I mean

something simpler. Suppose you want your hair cut, and as you walk

along the street you see a notice “hair-cutting, first floor”. It

is only by means of induction that you can _establish_ that this

_notice_ makes it in some degree probable that there is a hair-cutter’s

establishment on the first floor. I do not mean that you employ the

principle of induction; I mean that you act in accordance with it,

and that you would have to appeal to it if you were accompanied by a

long-haired sceptical philosopher who refused to go upstairs till he

was persuaded there was some point in doing so.

The principle of induction, _prima facie_, is as follows: Let there

be two kinds of events, A and B (_e.g._ lightning and thunder), and

let many instances be known in which an event of the kind A has

been quickly followed by one of the kind B, and no instances of the

contrary. Then either a sufficient number of instances of this

sequence, or instances of suitable kinds will make it increasingly

probable that A is always followed by B, and in time the probability

can be made to approach certainty without limit provided the right

kind and number of instances can be found. This is the principle we

have to examine. Scientific theories of induction generally try to

substitute well-chosen instances for numerous instances, and represent

number of instances as belonging to crude popular induction. But in

fact popular induction depends upon the emotional interest of the

instances, not upon their number. A child who has burnt its hand

_once_ in a candle-flame establishes an induction, but words take

longer, because at first they are not emotionally interesting. The

principle used in primitive practice is: Whatever, on a given occasion,

immediately precedes something very painful or pleasant, is a sign

of that interesting event. Number plays a secondary part as compared

with emotional interest. That is one reason why rational thought is so

difficult.

The logical problem of induction is to show that the proposition “A

is always accompanied (or followed) by B” can be rendered probable by

knowledge of instances in which this happens, provided the instances

are suitably chosen or very numerous. Far the best examination of

induction is contained in Mr. J. M. Keynes’s _Treatise on Probability_.

There is a valuable doctor’s thesis by the late Jean Nicod, _Le

Problème logique de l’induction_, which is very ably reviewed by R. B.

Braithwaite in _Mind_, October 1925. A man who reads these three will

know most of what is known about induction. The subject is technical

and difficult, involving a good deal of mathematics, but I will attempt

to give the gist of the results.

We will begin with the condition in which the problem had been left by

J. S. Mill. He had four canons of induction, by means of which, given

suitable examples, it could be demonstrated that A and B were causally

connected, if the law of causation could be assumed. That is to say,

given the law of causation, the scientific use of induction could

be reduced to deduction. Roughly the method is this: We know that B

must have a cause; the cause cannot be C or D or E, etc., because we

find by experiment or observation that these may be present without

producing B. On the other hand, we never succeed in finding A without

its being accompanied (or followed) by B. If A and B are both capable

of quantity, we may find further that the more there is of A the more

there is of B. By such methods we eliminate all possible causes except

A; therefore, since B must have a cause, that cause must be A. All

this is not really induction at all; true induction only comes in in

proving the law of causation. This law Mill regards as proved by mere

enumeration of instances: we know vast numbers of events which have

causes, and no events which can be shown to be uncaused; therefore, it

is highly probable that all events have causes. Leaving out of account

the fact that the law of causality cannot have quite the form that Mill

supposed, we are left with the problem: Does mere number of instances

afford a basis for induction? If not, is there any other basis? This is

the problem to which Mr. Keynes addresses himself.

Mr. Keynes holds that an induction may be rendered more probable by

number of instances, not because of their mere number, but because of

the probability, if the instances are very numerous, that they will

have nothing in common except the characteristics in question. We want,

let us suppose, to find out whether some quality A is always associated

with some quality B. We find instances in which this is the case; but

it may happen that in all our instances some quality C is also present,

and that it is C that is associated with B. If we can so choose our

instances that they have nothing in common except the qualities A and

B, then we have better grounds for holding that A is always associated

with B. If our instances are very numerous, then, even if we do not

_know_ that they have no other common quality, it may become quite

likely that this is the case. This, according to Mr. Keynes, is the

sole value of many instances.

A few technical terms are useful. Suppose we want to establish

inductively that there is some probability in favour of the

generalisation: “Everything that has the property _F_ also has the

property _f_”. We will call this generalisation _g_. Suppose we have

observed a number of instances in which _F_ and _f_ go together, and

no instances to the contrary. These instances may have other common

properties as well; the sum-total of their common properties is called

the _total positive analogy_, and the sum-total of their _known_ common

qualities is called the _known positive analogy_. The properties

belonging to some but not to all of the instances in question are

called the _negative analogy_: all of them constitute the _total

negative analogy_, all those that are _known_ constitute the _known

negative analogy_. To strengthen an induction, we want to diminish the

positive analogy to the utmost possible extent; this, according to Mr.

Keynes, is why numerous instances are useful.

On “pure” induction, where we rely solely upon number of instances,

without _knowing_ how they affect the analogy, Mr. Keynes concludes

(_Treatise in Probability_, p. 236):

“We have shown that if each of the instances necessarily follows

from the generalisation, then each additional instance increases the

probability of the generalisation, so long as the new instance could

not have been predicted with certainty from a knowledge of the former

instances.... The common notion, that each successive verification of

a doubtful principle strengthens it, is formally proved, therefore

without any appeal to conceptions of law or of causality. _But we have

not proved_ that this probability approaches certainty as a limit, or

even that our conclusion becomes more likely than not, as the number of

verifications or instances is indefinitely increased.”

It is obvious that induction is not much use unless, with suitable

care, its conclusions can be rendered more likely to be true than

false. This problem therefore necessarily occupies Mr. Keynes.

It is found that an induction will approach certainty as a limit if two

conditions are fulfilled:

(1) If the generalisation is false, the probability of its being true

in a new instance when it has been found to be true in a certain

number of instances, however great that number may be, falls short of

certainty by a finite amount.

(2) There is a finite _a priori_ probability in favour of our

generalisation.

Mr. Keynes uses “finite” here in a special sense. He holds that not all

probabilities are numerically measurable; a “finite” probability is one

which exceeds some numerically measurable probability however small.

_E.g._ our generalisation has a finite _a priori_ probability if it is

less unlikely than throwing heads a billion times running.

The difficulty is, however, that there is no easily discoverable way of

estimating the _a priori_ probability of a generalisation. In examining

this question, Mr. Keynes is led to a very interesting postulate

which, if true, will, he thinks, give the required finite _a priori_

probability. His postulate as he gives it is not quite correct, but I

shall give his form first, and then the necessary modification.

Mr. Keynes supposes that the qualities of objects cohere in groups,

so that the number of _independent_ qualities is much less than the

total number of qualities. We may conceive this after the analogy

of biological species: a cat has a number of distinctive qualities

which are found in all cats, a dog has a number of other distinctive

qualities which are found in all dogs. The method of induction can, he

says, be justified if we assume “that the objects in the field, over

which our generalisations extend, do not have an infinite number of

independent qualities; that, in other words, their characteristics,

however numerous, cohere together in groups of invariable connection,

which are finite in number” (p. 256). Again (p. 258): “As a biological

foundation for Analogy, therefore, we seem to need some such assumption

as that the amount of variety in the universe is limited in such a way

that there is no one object so complex that its qualities fall into an

infinite number of independent groups ... or rather that none of the

objects about which we generalise are as complex as this; or at least

that, though some objects may be infinitely complex, we sometimes have

a finite probability that an object about which we seek to generalise

is not infinitely complex.”

This postulate is called the “principle of limitation of variety”. Mr.

Keynes again finds that it is needed in attempts to establish laws

by statistics; if he is right, it is needed for all our scientific

knowledge outside pure mathematics. Jean Nicod pointed out that it is

not quite sufficiently stringent. We need, according to Mr. Keynes,

a finite probability that the object in question has only a finite

number of independent qualities; but what we really need is a finite

probability that the number of its independent qualities is less than

some assigned finite number. This is a very different thing, as may be

seen by the following illustration. Suppose there is some number of

which we know only that it is finite; it is infinitely improbable that

it will be less than a million, or a billion, or any other assigned

finite number, because, whatever such number we take, the number

of smaller numbers is finite and the number of greater numbers is

infinite. Nicod requires us to assume that there is a finite number _n_

such that there is a finite probability that the number of independent

qualities of our object is less than _n_. This is a much stronger

assumption than Mr. Keynes’s, which is merely that the number of

independent qualities is finite. It is the stronger assumption which is

needed to justify induction.

This result is very interesting and very important. It is remarkable

that it is in line with the trend of modern science. Eddington has

pointed out that there is a certain finite number which is fundamental

in the universe, namely the number of electrons. According to the

quantum theory, it would seem that the number of possible arrangements

of electrons may well also be finite, since they cannot move in all

possible orbits, but only in such as make the action in one complete

revolution conform to the quantum principle. If all this is true, the

principle of limitation of variety may well also be true. We cannot,

however, arrive at a proof of our principle in this way, because

physics uses induction, and is therefore presumably invalid unless

the principle is true. What we can say, in a general way, is that

the principle does not refute itself, but, on the contrary, leads to

results which confirm it. To this extent, the trend of modern science

may be regarded as increasing the plausibility of the principle.

It is important to realise the fundamental position of probability in

science. At the very best, induction and analogy only give probability.

Every inference worthy of the name is inductive, therefore all inferred

knowledge is at best probable. As to what is meant by probability,

opinions differ. Mr. Keynes takes it as a fundamental logical category:

certain premisses may make a conclusion more or less probable, without

making it certain. For him, probability is a relation between a premiss

and a conclusion. A proposition does not have a definite probability

on its own account; in itself, it is merely true or false. But it has

probabilities of different amounts in regard to different premisses.

When we speak, elliptically, of _the_ probability of a proposition,

we mean its probability in relation to all our relevant knowledge.

A proposition in probability cannot be refuted by mere observation:

improbable things may happen and probable things may fail to happen.

Nor is an estimate of probability relevant to given evidence proved

wrong when further evidence alters the probability.

For this reason the inductive principle cannot be proved or disproved

by experience. We might prove validly that such and such a conclusion

was enormously probable, and yet it might not happen. We might

prove invalidly that it was probable, and yet it might happen.

What happens affects the probability of a proposition, since it is

relevant evidence; but it never alters the probability relative to

the previously available evidence. The whole subject of probability,

therefore, on Mr. Keynes’s theory, is strictly _a priori_ and

independent of experience.

There is however another theory, called the “frequency theory”, which

would make probability not indefinable, and would allow empirical

evidence to affect our estimates of probability relative to given

premisses. According to this theory in its crude form, the probability

that an object having the property _F_ will have the property _f_ is

simply the proportion of the objects having both properties to all

those having the property _F_. For example, in a monogamous country

the probability of a married person being male is exactly a half. Mr.

Keynes advances strong arguments against all forms of this theory that

existed when his book was written. There is however an article by R. H.

Nisbet on “The Foundations of Probability” in _Mind_ for January 1926,

which undertakes to rehabilitate the frequency theory. His arguments

are interesting, and suffice to show that the controversy is still an

open one, but they do not, in my opinion, amount to decisive proof.

It is to be observed, however, that the frequency theory, if it could

be maintained, would be preferable to Mr. Keynes’s, because it would

get rid of the necessity for treating probability as indefinable, and

would bring probability into much closer touch with what actually

occurs. Mr. Keynes leaves an uncomfortable gap between probability and

fact, so that it is far from clear why a rational man will act upon a

probability. Nevertheless, the difficulties of the frequency theory

are so considerable that I cannot venture to advocate it definitely.

Meanwhile, the details of the discussion are unaffected by the view

we may take on this fundamental philosophical question. And on either

view the principle of limitation of variety will be equally necessary

to give validity to the inferences by induction and analogy upon which

science and daily life depend.

CHAPTER XXVI

EVENTS, MATTER, AND MIND

Everything in the world is composed of “events”; that, at least, is the

thesis I wish to maintain. An “event”, as I understand it, is something

having a small finite duration and a small finite extension in space;

or rather, in view of the theory of relativity, it is something

occupying a small finite amount of space-time. If it has parts, these

parts, I say, are again events, never something occupying a mere point

of instant, whether in space, in time, or in space-time. The fact that

an event occupies a finite amount of space-time does not prove that it

has parts. Events are not impenetrable, as matter is supposed to be; on

the contrary, every event in space-time is overlapped by other events.

There is no reason to suppose that any of the events with which we are

familiar are infinitely complex; on the contrary, everything known

about the world is compatible with the view that every complex event

has a finite number of parts. We do not know that this is the case,

but it is an hypothesis which cannot be refuted and is simpler than

any other possible hypothesis. I shall therefore adopt it as a working

hypothesis in what follows.

When I speak of an “event” I do not mean anything out of the way.

Seeing a flash of lightning is an event; so is hearing a tire burst,

or smelling a rotten egg, or feeling the coldness of a frog. These

are events that are “data” in the sense of Chapter XXV; but, on the

principles explained in that chapter, we infer that there are events

which are not data and happen at a distance from our own body. Some of

these are data to other people, others are data to no one. In the case

of the flash of lightning, there is an electro-magnetic disturbance

consisting of events travelling outward from the place where the flash

takes place, and then when this disturbance reaches the eye of a

person or animal that can see, there is a percept, which is causally

continuous with the events between the place of the lightning and the

body of the percipient. Percepts afford the logical premisses for all

inferences to events that are not precepts, wherever such inferences

are logically justifiable. Particular colours and sounds and so on are

events; their causal antecedents in the inanimate world are also events.

If we assume, as I propose to do, that every event has only a finite

number of parts, then every event is composed of a finite number of

events that have no parts. Such events I shall call “minimal events.”

It will simplify our discussion to assume them, but by a little

circumlocution this assumption could be eliminated. The reader must not

therefore regard it as an essential part of what follows.

A minimal event occupies a finite region in space-time. Let us take

time alone for purposes of illustration. The event in question may

overlap in time with each of two others, although the first of these

others wholly precedes the second; for example, you may hear a long

note on the violin while you hear two short notes on the piano. (It

is not necessary to suppose that these are really minimal events; I

merely want to illustrate what is meant.) I assume that every event

is contemporaneous with events that are not contemporaneous with each

other; this is what is meant by saying that every event lasts for a

finite time, as the reader can easily convince himself if he remembers

that time is wholly relational. If we look away from the world of

physics for a moment, and confine ourselves to the world of one man’s

experience, we can easily define an “instant” in his life. It will be

a group of events, all belonging to his experience, and having the

following two properties: (1) any two of the events overlap; (2) no

event outside the group overlaps with every member of the group. By

a slightly more complicated but essentially similar method, we can

define a point-instant in space-time as a group of events having two

properties analogous to those used just now in defining an “instant”

in one biography.[13] Thus the “points” (or point-instants) that

the mathematician needs are not simple, but are structures composed

of events, made up for the convenience of the mathematician. There

will be many “points” of which a given minimal event is a member;

all these together make up the region of space-time occupied by that

event. Space-time order, as well as space-time points, results from the

relations between events.

[13] See _The Analysis of Matter_, by the present author,

chap. xxviii.

A piece of matter, like a space-time point, is to be constructed out of

events, but the construction is considerably more complicated, and in

the end is only an approximation to what the physicist supposes to be

really taking place. There are, at the moment, two somewhat different

views of matter, one appropriate to the study of atomic structure, the

other to the general theory of relativity as affording an explanation

of gravitation. The view appropriate to atomic structure has itself

two forms, one derived from Heisenberg, the other from De Broglie

and Schrödinger. These two forms, it is true, are mathematically

equivalent, but in words they are very different. Heisenberg regards

a piece of matter as a centre from which radiations travel outward;

the radiations are supposed really to occur, but the matter at their

centre is reduced to a mere mathematical fiction. The radiations are,

for example, such as constitute light; they are all avowedly systems

of events, not changes in the conditions or relations of “substances.”

In the De Broglie-Schrödinger system, matter consists of wave motions.

It is not necessary to the theory to postulate anything about these

wave-motions except their mathematical characteristics, but, obviously,

since they are to explain matters they cannot serve their purpose if

they consist of motions of matter. In this system also, therefore,

we are led to construct matter out of systems of events, which just

happen, and do not happen “to” matter or “to” anything else.

Gravitation, as explained by the general theory of relativity, is

reduced to “crinkles” in space-time. Space-time being, as we have

already seen, a system constructed out of events, the “crinkles” in it

are also derived from events. There is no reason to suppose that there

is a “thing” at the place where the “crinkle” is most crinkly. Thus in

this part of physics, also, matter has ceased to be a “thing” and has

become merely a mathematical characteristic of the relations between

complicated logical structures composed of events.

It was traditionally a property of substance to be permanent, and to a

considerable extent matter has retained this property in spite of its

loss of substantiality. But its permanence now is only approximate,

not absolute. It is thought that an electron and a proton can meet and

annihilate each other; in the stars this is supposed to be happening

on a large scale.[14] And even while an electron or a proton lasts,

it has a different kind of persistence from that formerly attributed

to matter. A wave in the sea persists for a longer or shorter time:

the waves that I see dashing themselves to pieces on the Cornish coast

may have come all the way from Brazil, but that does not mean that a

“thing” has travelled across the Atlantic; it means only that a certain

process of change has travelled. And just as a wave in the sea comes

to grief at last on the rocks, so an electron or a proton may come to

grief when it meets some unusual state of affairs.

[14] See _The Analysis of Matter_, by the present author,

chap. xxviii.

Thus “matter” has very definitely come down in the world as a result of

recent physics. It used to be the cause of our sensations: Dr. Johnson

“disproved” Berkeley’s denial of matter by kicking a stone. If he had

known that his foot never touched the stone, and that both were only

complicated systems of wave-motions, he might have been less satisfied

with his refutation. We cannot say that “matter” is the cause of our

sensations. We can say that the events which cause our sensations

usually belong to the sort of group that physicists regard as material;

but that is a very different thing. Impenetrability used to be a noble

property of matter, a kind of Declaration of Independence; now it is a

merely tautological result of the way in which matter is defined. The

events which are the real stuff of the world are not impenetrable,

since they can overlap in space-time. In a word, “matter” has become

no more than a convenient shorthand for stating certain causal laws

concerning events.

But if matter has fared badly, mind has fared little better.

The adjective “mental” is one which is not capable of any exact

significance. There is, it is true, an important group of events,

namely percepts, all of which may be called “mental”. But it would be

arbitrary to say that there are no “mental” events except percepts,

and yet it is difficult to find any principle by which we can decide

what other events should be included. Perhaps the most essential

characteristics of mind are introspection and memory. But memory

in some of its forms is, as we have seen, a consequence of the law

of conditioned reflexes, which is at least as much physiological

as psychological, and characterises living tissue rather than

mind. Knowledge, as we have found, is not easy to distinguish from

sensitivity, which is a property possessed by scientific instruments.

Introspection is a form of knowledge, but turns out, on examination, to

be little more than a cautious interpretation of ordinary “knowledge”.

Where the philosopher’s child at the Zoo says “There is a hippopotamus

over there”, the philosopher should reply: “There is a coloured pattern

of a certain shape, which may perhaps be connected with a system of

external causes of the sort called a hippopotamus”. (I do not live up

to this precept myself.) In saying that there is a coloured pattern,

the philosopher is practising introspection in the only sense that I

can attach to that term, _i.e._ his knowledge-reaction is to an event

situated in his own brain from the standpoint of physical space, and

is consciously avoiding physiological and other inference as far as

possible. Events to which a knowledge-reaction of this sort occurs are

“mental”; so are, presumably, other events resembling them in certain

respects. But I do not see any way of defining this wider group except

by saying that mental events are events in a living brain, or, better,

in a region combining sensitivity and the law of learned reactions to

a marked extent. This definition has at least the merit of showing that

mentality is an affair of causal laws, not of the quality of single

events, and also that mentality is a matter of degree.

Perhaps it is not unnecessary to repeat, at this point, that events in

the brain are not to be regarded as consisting of motions of bits of

matter. Matter and motion, as we have seen, are logical constructions

using events as their material, and events are therefore something

quite different from matter in motion. I take it that, when we have

a percept, just what we perceive (if we avoid avoidable sources of

error) is an event occupying part of the region which, for physics, is

occupied by the brain. In fact, perception gives us the most concrete

knowledge we possess as to the stuff of the physical world, but what

we perceive is part of the stuff of our brains, not part of the stuff

of tables and chairs, sun, moon, and stars. Suppose we are looking at

a leaf, and we see a green patch. This patch is not “out there” where

the leaf is, but is an event occupying a certain volume in our brains

during the time that we see the leaf. Seeing the leaf consists of

the existence, in the region occupied by our brain, of a green patch

causally connected with the leaf, or rather with a series of events

emanating from the place in physical space where physics places the

leaf. The percept is one of this series of events, differing from the

others in its effects owing to the peculiarities of the region in

which it occurs--or perhaps it would be more correct to say that the

different effects _are_ the peculiarities of the region.

Thus “mind” and “mental” are merely approximate concepts, giving a

convenient shorthand for certain approximate laws. In a completed

science, the word “mind” and the word “matter” would both disappear,

and would be replaced by causal laws concerning “events”, the only

events known to us otherwise than in their mathematical and causal

properties being percepts, which are events situated in the same

region as a brain and having effects of a peculiar sort called

“knowledge-reactions”.

It will be seen that the view which I am advocating is neither

materialism nor mentalism, but what we call “neutral monism”. It is

monism in the sense that it regards the world as composed of only one

_kind_ of stuff, namely events; but it is pluralism in the sense that

it admits the existence of a great multiplicity of events, each minimal

event being a logically self-subsistent entity.

There is, however, another question, not quite the same as this, namely

the question as to the relations of psychology and physics. If we knew

more, would psychology be absorbed in physics? or, conversely, would

physics be absorbed in psychology? A man may be a materialist and

yet hold that psychology is an independent science; this is the view

taken by Dr. Broad in his important book on _The Mind and its Place

in Nature_. He holds that a mind is a material structure, but that it

has properties which could not, even theoretically, be inferred from

those of its material constituents. He points out that structures very

often have properties which, in the present state of our knowledge,

cannot be inferred from the properties and relations of their parts.

Water has many properties which we cannot infer from those of hydrogen

and oxygen, even if we suppose ourselves to know the structure of the

molecule of water more completely than we do as yet. Properties of a

whole which cannot, even theoretically, be inferred from the properties

and relations of its parts are called by Dr. Broad “emergent”

properties. Thus he holds that a mind (or brain) has properties which

are “emergent”, and to this extent psychology will be independent of

physics and chemistry. The “emergent” properties of minds will only be

discoverable by observation of minds, not by inference from the laws

of physics and chemistry. This possibility is an important one, and it

will be worth while to consider it.

Our decision to regard a unit of matter as itself not ultimate, but an

assemblage of events, somewhat alters the form of our question as to

“emergent” properties. We have to ask: Is matter emergent from events?

Is mind emergent from events? If the former, is mind emergent from

matter, or deducible from the properties of matter, or neither? If the

latter, is matter emergent from mind or deducible from the properties

of mind, or neither? Of course, if neither mind nor matter is emergent

from events, these latter questions do not arise.

Let us coin a word, “chrono-geography”, for the science which begins

with events having space-time relations and does not assume at the

outset that certain strings of them can be treated as persistent

material units or as minds. Then we have to ask ourselves first: can

the science of matter, as it appears in physics and chemistry, be

wholly reduced to chrono-geography? If no, matter is emergent from

events; if yes, it is not emergent.

_Is matter emergent from events?_ In the present state of science it

is difficult to give a decided answer to this question. The notion

of matter, in modern physics, has become absorbed into the notion of

energy. Eddington, in his _Mathematical Theory of Relativity_ shows

that, in virtue of the laws assumed concerning events, there must

be something having the observed properties of matter and energy as

regards conservation. This he calls the “material-energy-tensor”, and

suggests that it is the reality which we sometimes call “matter” and

sometimes “energy”. To this extent, matter has been shown to be not

emergent. But the existence of electrons and protons (to the extent

that they do exist) has not yet been deduced from the general theory

of relativity, though attempts are being made and may at any moment

succeed. If and when these attempts succeed, physics will cease to be

in any degree independent of chrono-geography, but for the present

it remains in part independent. As for chemistry, although we cannot

practically reduce it all to physics, we can see how, theoretically,

this could be done, and I think it is safe to assume that it is not an

ultimately independent science.

The question we have been asking is: could we predict, theoretically,

from the laws of events that there must be material units obeying

the laws which they do in fact obey, or is this a new, logically

independent, fact? In theory we might be able to prove that it is _not_

independent, but it would be very difficult to prove that it _is_. The

present position is, broadly speaking, that the continuous properties

of the physical world can be deduced from chrono-geography, but not the

discontinuous facts, viz. electrons and protons and Planck’s quantum.

Thus for the present materiality is practically, though perhaps not

theoretically, an emergent characteristic of certain groups of events.

_Is mind emergent from events?_ This question, as yet, can hardly be

even discussed intelligently, because psychology is not a sufficiently

advanced science. There are, nevertheless, some points to be noted.

Chrono-geography is concerned only with the abstract mathematical

properties of events, and cannot conceivably, unless it is radically

transformed, prove that there are visual events, or auditory events, or

events of any of the kinds that we know by perception. In this sense,

psychology is certainly emergent from chrono-geography and also from

physics, and it is hard to see how it can ever cease to be so. The

reason for this is that our knowledge of data contains features of a

qualitative sort, which cannot be deduced from the merely mathematical

features of the space-time events inferred from data, and yet these

abstract mathematical features are all that we can legitimately infer.

The above argument decides also that mind must be emergent from matter,

if it is a material structure. No amount of physics can ever tell us

all that we do in fact know about our own percepts.

We have still to ask whether we are to regard a mind as a structure of

material units or not. If we do so regard it, we are, so far as mind is

concerned, emergent materialists in view of what we have just decided;

this is the view favoured by Dr. Broad. If we do not so regard it, we

are in no sense materialists. In favour of the materialist view, there

is the fact that, so far as our experience goes, minds only emerge in

connection with certain physical structures, namely living bodies, and

that mental development increases with a certain kind of complexity

of physical structure. We cannot set against this the argument that

minds have peculiar characteristics, for this is quite consistent with

_emergent_ materialism. If we are to refute it, it must be by finding

out what sort of group of events constitutes a mind. It is time to

address ourselves to this question.

_What is a mind?_ It is obvious, to begin with, that a mind must be a

group of mental events, since we have rejected the view that it is a

single simple entity such as the ego was formerly supposed to be. Our

first step, therefore, is to be clear as to what we mean by a “mental”

event.

We said a few pages ago that: _Mental events are events in a region

combining sensitivity and the law of learned reactions to a marked

extent_. For practical purposes, this means (subject to a proviso to be

explained shortly) that a mental event is any event in a living brain.

We explained that this does not mean that a mental event consists of

matter in motion, which is what an old-fashioned physicist would regard

as the sort of event that happens in a brain. Matter in motion, we have

seen, is not an event in our sense, but a shorthand description of a

very complicated causal process among events of a different sort. But

we must say a few words in justification of our definition.

Let us consider some alternative definitions. A mental event, we might

say, is one which is “experienced.” When is an event “experienced”?

We might say: when it has “mnemic” effects, _i.e._ effects governed

by the law of association. But we saw that this law applies to purely

bodily events such as the contraction of the pupil, with which nothing

“mental” seems to be connected. Thus if our definition is to serve,

we shall have to define “experience” differently; we shall have to

say that the mnemic effects must include something that can be called

“knowledge.” This would suggest the definition: A mental event is

anything that is remembered. But this is too narrow: we only remember

a small proportion of our mental events. We might have regarded

“consciousness” as the essence of mental events, but this view was

examined and found inadequate in Chapter XX. Moreover, we do not want

our definition to exclude the “unconscious”.

It is clear that the primary mental events, those about which there can

be no question, are percepts. But percepts have certain peculiar causal

properties, notably that they give rise to knowledge-reactions, and

that they are capable of having mnemic effects which are cognitions.

These causal properties, however, belong to some events which are not

apparently percepts. It seems that any event in the brain may have

these properties. And perhaps we were too hasty in saying that the

contraction of the pupil on hearing a loud noise involves nothing

“mental”. There may be other “mental” events connected with a human

body besides those belonging to the central personality. I shall come

back to this possibility presently. Meanwhile, I shall adhere to the

above definition of a “mental” event, which, as we saw, makes mentality

a matter of degree.

We can now return to the question: What is a mind? There may be mental

events not forming part of the sort of group that we should call a

“mind”, but there certainly are groups having that kind of unity that

make us call them one mind. There are two marked characteristics of

a mind: First, it is connected with a certain body; secondly, it has

the unity of one “experience”. The two _prima facie_ diverge in cases

of dual or multiple personality, but I think this is more apparent

than real. These two characteristics are, one physical, the other

psychological. Let us consider each in turn as a possible definition of

what we mean by one “mind”.

In the physical way, we begin by observing that every mental event

known to us is also part of the history of a living body, and we define

a “mind” as the group of mental events which form part of the history

of a certain living body. The definition of a living body is chemical,

and the reduction of chemistry to physics is clear in theory, though

in practice the mathematics is too difficult. It is so far a merely

empirical fact that mnemic causation is almost exclusively associated

with matter having a certain chemical structure. But the same may be

said of magnetism. As yet, we cannot deduce the magnetic properties of

iron from what we know of the structure of the atom of iron, but no one

doubts that they could be deduced by a person with sufficient knowledge

and sufficient mathematical skill. In like manner it may be assumed

that mnemic causation is theoretically deducible from the structure of

living matter. If we knew enough, we might be able to infer that some

other possible structure would exhibit mnemic phenomena, perhaps in an

even more marked degree; if so, we might be able to construct Robots

who would be more intelligent than we are.

In the psychological way of defining a “mind”, it consists of all the

mental events connected with a given mental event by “experience”,

_i.e._ by mnemic causation, but this definition needs a little

elaboration before it can be regarded as precise. We do not want the

contraction of the pupil to count as a “mental” event; therefore a

mental event will have to be one which has mnemic effects, not merely

mnemic causes. In that case, however, there cannot be a last mental

event in a man’s life, unless we assume that it may have mnemic effects

on his body after death. Perhaps we may avoid this inconvenience by

discovering the _kind_ of event that usually has mnemic effects, though

they may be prevented from occurring by special circumstances. Or we

might maintain that death is gradual, even when it is what is called

instantaneous; in that case the last events in a man’s life grow

progressively less mental as life ebbs. Neglecting this point, which is

not very important, we shall define the “experience” to which a given

mental event belongs as all those mental events which can be reached

from the given event by a mnemic causal chain, which may go backwards

or forwards, or alternately first one and then the other. This may be

conceived on the analogy of an engine shunting at a junction or where

there are many points: any line that can be reached, by however many

shuntings, will count as part of the same experience.

We cannot be sure that all the mental events connected with one body

are connected by links of mnemic causation with each other, and

therefore we cannot be sure that our two definitions of one “mind”

give the same result. In cases of multiple personality, some at least

of the usual mnemic effects, notably recollection, are absent in the

life of one personality when they have occurred in the life of the

other. But probably both personalities are connected by mnemic chains

with events which occurred before the dissociation took place, so that

there would be only one mind according to our definition. But there

are other possibilities which must be considered. It may be that each

cell in the body has its own mental life, and that only selections from

these mental lives go to make up the life which we regard as ours.

The “unconscious” might be the mental lives of subordinate parts of

the body, having occasional mnemic effects which we can notice, but

in the main separate from the life of which we are “conscious”. If

so, the mental events connected with one body will be more numerous

than the events making up its central “mind”. These, however, are only

speculative possibilities.

I spoke a moment ago of the life of which we are “conscious”, and

perhaps the reader has been wondering why I have not made more use of

the notion of “consciousness”. The reason is that I regard it as only

one kind of mnemic effect, and not one entitled to a special place.

To say that I am “conscious” of an event is to say that I recollect

it, at any rate for a short time after it has happened. To say that I

recollect an event is to say that a certain event is occurring in me

now which is connected by mnemic causation with the event recollected,

and is of the sort that we call a “cognition” of that event. But

events which I do not recollect may have mnemic effects upon me. This

is the case, not only where we have Freudian suppression, but in all

habits which were learnt long ago and have now become automatic, such

as writing and speaking. The emphasis upon consciousness has made a

mystery of the “unconscious”, which ought to be in no way surprising.

It does not much matter which of our two definitions of a “mind” we

adopt. Let us, provisionally, adopt the first definition, so that a

mind is all the mental events which form part of the history of a

certain living body, or perhaps we should rather say a living brain.

We can now tackle the question which is to decide whether we are

emergent materialists or not, namely:

_Is a mind a structure of material units?_

I think it is clear that the answer to this question is in the

negative. Even if a mind consists of all the events in a brain, it

does not consist of bundles of these events grouped as physics groups

them, _i.e._ it does not lump together all the events that make up

one piece of matter in the brain, and then all the events that make

up another, and so on. Mnemic causation is what concerns us most in

studying mind, but this seems to demand a recourse to physics, if we

assume, as seems plausible, that mental mnemic causation is due to

effects upon the brain. This question, however, is still an open one.

If mnemic causation is ultimate, mind is emergent. If not, the question

is more difficult. As we saw earlier, there certainly is knowledge in

psychology which cannot ever form part of physics. But as this point is

important, I shall repeat the argument in different terms.

The difference between physics and psychology is analogous to that

between a postman’s knowledge of letters and the knowledge of a

recipient of letters. The postman knows the movements of many letters,

the recipient knows the contents of a few. We may regard the light and

sound waves that go about the world as letters of which the physicist

may know the destination; some few of them are addressed to human

beings, and when read give psychological knowledge. Of course the

analogy is not perfect, because the letters with which the physicist

deals are continually changing during their journeys, as if they were

written in fading ink, which, also, was not quite dry all the time,

but occasionally got smudged with rain. However, the analogy may pass

if not pressed.

It would be possible without altering the detail of previous

discussions, except that of Chapter XXV, to give a different turn

to the argument, and make matter a structure composed of mental

units. I am not quite sure that this is the wrong view. It arises not

unnaturally from the argument as to data contained in Chapter XXV. We

saw that all data are mental events in the narrowest and strictest

sense, since they are percepts. Consequently all verification of causal

laws consists in the occurrence of expected percepts. Consequently any

inference beyond percepts (actual or possible) is incapable of being

empirically tested. We shall therefore be prudent if we regard the

non-mental events of physics as mere auxiliary concepts, not assumed

to have any reality, but only introduced to simplify the laws of

percepts. Thus matter will be a construction built out of percepts, and

our metaphysic will be essentially that of Berkeley. If there are no

non-mental events, causal laws will be very odd; for example, a hidden

dictaphone may record a conversation although it did not exist at the

time, since no one was perceiving it. But although this seems odd, it

is not logically impossible. And it must be conceded that it enables

us to interpret physics with a smaller amount of dubious inductive and

analogical inference than is required if we admit non-mental events.

In spite of the logical merits of this view, I cannot bring myself

to accept it, though I am not sure that my reasons for disliking it

are any better than Dr. Johnson’s. I find myself constitutionally

incapable of believing that the sun would not exist on a day when he

was everywhere hidden by clouds, or that the meat in a pie springs into

existence at the moment when the pie is opened. I know the logical

answer to such objections, and _qua logician_ I think the answer a good

one. The logical argument, however, does not even tend to show that

there are _not_ non-mental events; it only tends to show that we have

no right to feel sure of their existence. For my part, I find myself

in fact believing in them in spite of all that can be said to persuade

me that I ought to feel doubtful.

There is an argument, of a sort, against the view we are considering.

I have been assuming that we admit the existence of other people and

their perceptions, but question only the inference from perceptions to

events of a different kind. Now there is no good reason why we should

not carry our logical caution a step further. I cannot verify a theory

by means of another man’s perceptions, but only by means of my own.

Therefore the laws of physics can only be verified by me in so far as

they lead to predictions of _my_ percepts. If then, I refuse to admit

non-mental events because they are not verifiable, I ought to refuse

to admit mental events in every one except myself, on the same ground.

Thus I am reduced to what is called “solipsism”, _i.e._ the theory that

I alone exist. This is a view which is hard to refute, but still harder

to believe. I once received a letter from a philosopher who professed

to be a solipsist, but was surprised that there were no others! Yet

this philosopher was by way of believing that no one else existed. This

shows that solipsism is not really believed even by those who think

they are convinced of its truth.

We may go a step further. The past can only be verified indirectly,

by means of its effects in the future; therefore the type of logical

caution we have been considering should lead us to abstain from

asserting that the past really occurred: we ought to regard it as

consisting of auxiliary concepts convenient in stating the laws

applicable to the future. And since the future, though verifiable if

and when it occurs, is as yet unverified, we ought to suspend judgment

about the future also. If we are not willing to go so far as this,

there seems no reason to draw the line at the precise point where it

was drawn by Berkeley. On these grounds I feel no shame in admitting

the existence of non-mental events such as the laws of physics lead us

to infer. Nevertheless, it is important to realise that other views are

tenable.

CHAPTER XXVII

MAN’S PLACE IN THE UNIVERSE

In this final chapter, I propose to recapitulate the main conclusions

at which we have arrived, and then to say a few words on the subject of

Man’s relation to the universe in so far as philosophy has anything to

teach on this subject without extraneous help.

Popular metaphysics divides the known world into mind and matter, and

a human being into soul and body. Some--the materialists--have said

that matter alone is real and mind is an illusion. Many--the idealists

in the technical sense, or mentalists, as Dr. Broad more appropriately

calls them--have taken the opposite view, that mind alone is real and

matter is an illusion. The view which I have suggested is that both

mind and matter are structures composed of a more primitive stuff which

is neither mental nor material. This view, called “neutral monism”,

is suggested in Mach’s _Analysis of Sensations_, developed in William

James’s _Essays in Radical Empiricism_, and advocated by John Dewey,

as well as by Professor R. B. Parry and other American realists. The

use of the word “neutral” in this way is due to Dr. H. M. Sheffer,[15]

formerly of Harvard, who is one of the ablest logicians of our time.

[15] See Holt’s _Concept of Consciousness_, preface.

Since man is the instrument of his own knowledge, it is necessary to

study him as an instrument before we can appraise the value of what our

senses seem to tell us concerning the world. In Part I we studied man,

within the framework of common-sense beliefs, just as we might study

clocks or thermometers, as an instrument sensitive to certain features

of the environment, since sensitiveness to the environment is obviously

an indispensable condition for knowledge about it.

In Part II we advanced to the study of the physical world. We

found that matter, in modern science, has lost its solidity and

substantiality; it has become a mere ghost haunting the scenes of

its former splendours. In pursuit of something that could be treated

as substantial, physicists analysed ordinary matter into molecules,

molecules into atoms, atoms into electrons and protons. There, for

a few years, analysis found a resting-place. But now electrons and

protons themselves are dissolved into systems of radiations by

Heisenberg, and into systems of waves by Schrödinger--the two theories

amount mathematically to much the same thing. And these are not wild

metaphysical speculations; they are sober mathematical calculations,

accepted by the great majority of experts.

Another department of theoretical physics, the theory of relativity,

has philosophical consequences which are, if possible, even more

important. The substitution of space-time for space and time has

made the category of substance less applicable than formerly, since

the essence of substance was persistence through time, and there is

now no one cosmic time. The result of this is to turn the physical

world into a four-dimensional continuum of events, instead of a

series of three-dimensional states of a world composed of persistent

bits of matter. A second important feature of relativity-theory is

the abolition of force, particularly gravitational force, and the

substitution of differential causal laws having to do only with the

neighbourhood of an event, not with an influence exerted from a

distance, such as gravitation formerly seemed to be.

The modern study of the atom has had two consequences which have

considerably changed the philosophical hearing of physics. On the

one hand, it appears that there are discontinuous changes in nature,

occasions when there is a sudden jump from one state to another without

passing through the intermediate states. (Schrödinger, it is true,

questions the need for assuming discontinuity; but so far his opinion

has not prevailed.) On the other hand, the course of nature is not so

definitely determined by the physical laws at present known as it was

formerly thought to be. We cannot predict when a discontinuous change

will take place in a given atom, though we can predict statistical

averages. It can no longer be said that, given the laws of physics and

the relevant facts about the environment, the future history of an atom

can theoretically be calculated from its present condition. It may be

that this is merely due to the insufficiency of our knowledge, but we

cannot be sure that this is the case. As things stand at present, the

physical world is not so rigidly deterministic as it has been believed

to be during the last 250 years. And in various directions what

formerly appeared as laws governing each separate atom are now found to

be only averages attributable in part to the laws of chance.

From these questions concerning the physical world in itself, we were

led to others concerning the causation of our perceptions, which are

the data upon which our scientific knowledge of physics is based. We

saw that a long causal chain always intervenes between an external

event and the event in us which we regard as perception of the

external event. We cannot therefore suppose that the external event

is exactly what we see or hear; it can, at best, resemble the percept

only in certain structural respects. This fact has caused considerable

confusion in philosophy, partly because philosophers tried to think

better of perception than it deserves, partly because they failed to

have clear ideas on the subject of space. It is customary to treat

space as a characteristic of matter as opposed to mind, but this is

only true of _physical_ space. There is also _perceptual_ space,

which is that in which what we know immediately through the senses is

situated. This space cannot be identified with that of physics. From

the standpoint of physical space, all our percepts are in our heads;

but in perceptual space our percept of our hand is outside our percept

of our head. The failure to keep physical and perceptual space distinct

has been a source of great confusion in philosophy.

In Part III we resumed the study of man, but now as he appears to

himself, not only as he is known to an external observer. We decided,

contrary to the view of the behaviourists, that there are important

facts which cannot be known except when the observer and observed are

the same person. The datum in perception, we decided, is a private fact

which can only be known directly to the percipient; it is a datum for

physics and psychology equally, and must be regarded as both physical

and mental. We decided later that there are inductive grounds, giving

probability but not certainty, in favour of the view that perceptions

are causally connected with events which the percipient does not

experience, which may belong only to the physical world.

The behaviour of human beings is distinguished from that of inanimate

matter by what are called “mnemic” phenomena, _i.e._ by a certain kind

of effect of past occurrences. This kind of effects is exemplified in

memory, in learning, in the intelligent use of words, and in every

kind of knowledge. But we cannot, on this ground, erect an absolute

barrier between mind and matter. In the first place, inanimate matter,

to some slight extent, shows analogous behaviour--_e.g._ if you unroll

a roll of paper, it will roll itself up again. In the second place, we

find that living bodies display mnemic phenomena to exactly the same

extent to which minds display them. In the third place, if we are to

avoid what I have called “mnemic” causation, which involves action at

a distance in time, we must say that mnemic phenomena in mental events

are due to the modification of the body by past events. That is to

say, the set of events which constitutes one man’s experience is not

causally self-sufficient, but is dependent upon causal laws involving

events which he cannot experience.

On the other hand, our knowledge of the physical world is purely

abstract: we know certain logical characteristics of its structure,

but nothing of its intrinsic character. There is nothing in physics

to prove that the intrinsic character of the physical world differs,

in this or that respect, from that of the mental world. Thus from

both ends, both by the analysis of physics and by the analysis of

psychology, we find that mental and physical events form one causal

whole, which is not known to consist of two different sorts. At

present, we know the laws of the physical world better than those of

the mental world, but that may change. We know the intrinsic character

of the mental world to some extent, but we know absolutely nothing

of the intrinsic character of the physical world. And in view of the

nature of the inferences upon which our knowledge of physics rests, it

seems scarcely possible that we should ever know more than abstract

laws about matter.

In Part IV we considered what philosophy has to say about the universe.

The function of philosophy, according to the view advocated in this

volume, is somewhat different from that which has been assigned to it

by a large and influential school. Take, _e.g._ Kant’s antinomies.

He argues (1) that space must be infinite, (2) that space cannot be

infinite; and he deduces that space is subjective. The non-Euclideans

refuted the argument that it must be infinite, and Georg Cantor refuted

the argument that it cannot be. Formerly, _a priori_ logic was used to

prove that various hypotheses which looked possible were impossible,

leaving only one possibility, which philosophy therefore pronounced

true. Now _a priori_ logic is used to prove the exact contrary, namely,

that hypotheses which looked impossible are possible. Whereas logic

was formerly counsel for the prosecution, it is now counsel for the

defence. The result is that many more hypotheses are at large than

was formerly the case. Formerly, to revert to the instance of space,

it appeared that experience left only one kind of space to logic, and

logic showed this one kind to be impossible. Now, logic presents many

kinds of space as possible apart from experience, and experience only

partially decides between them. Thus, while our knowledge of what is

has become less than it was formerly supposed to be, our knowledge of

what may be is enormously increased. Instead of being shut in within

narrow walls, of which every nook and cranny could be explored, we find

ourselves in an open world of free possibilities, where much remains

unknown because there is so much to know. The attempt to prescribe

to the universe by means of _a priori_ principles has broken down;

logic, instead of being, as formerly, a bar to possibilities, has

become the great liberator of the imagination, presenting innumerable

alternatives which are closed to unreflective common sense, and leaving

to experience the task of deciding, where decision is possible, between

the many worlds which logic offers for our choice.

Philosophical knowledge, if what we have been saying is correct, does

not differ essentially from scientific knowledge; there is no special

source of wisdom which is open to philosophy but not to science, and

the results obtained by philosophy are not radically different from

those reached in science. Philosophy is distinguished from science only

by being more critical and more general. But when I say that philosophy

is critical, I do not mean that it attempts to criticise knowledge from

outside, for that would be impossible: I mean only that it examines

the various parts of our supposed knowledge to see whether they are

mutually consistent and whether the inferences employed are such as

seem valid to a careful scrutiny. The criticism aimed at is not that

which, without reason, determines to reject, but that which considers

each piece of apparent knowledge on its merits and retains whatever

still appears to be knowledge when this consideration is completed.

That some risk of error remains must be admitted, since human beings

are fallible. Philosophy may claim justly that it diminishes the risk

of error, and that in some cases it renders the risk so small as to be

practically negligible. To do more than this is not possible in a world

where mistakes must occur; and more than this no prudent advocate of

philosophy would claim to have performed.

I want to end with a few words about man’s place in the universe. It

has been customary to demand of a philosopher that he should show that

the world is good in certain respects. I cannot admit any duty of this

sort. One might as well demand of an accountant that he should show

a satisfactory balance sheet. It is just as bad to be fraudulently

optimistic in philosophy as in money matters. If the world is good,

by all means let us know it; but if not, let us know that. In any

case, the question of the goodness or badness of the world is one for

science rather than for philosophy. We shall call the world good if

it has certain characteristics that we desire. In the past philosophy

professed to be able to prove that the world had such characteristics,

but it is now fairly evident that the proofs were invalid. It does not,

of course, follow that the world does not have the characteristics in

question; it follows only that philosophy cannot decide the problem.

Take for example the problem of personal immortality. You may believe

this on the ground of revealed religion, but that is a ground which

lies outside philosophy. You may believe it on the ground of the

phenomena investigated by psychical research, but that is science, not

philosophy. In former days, you could believe it on a philosophical

ground, namely, that the soul is a substance and all substances are

indestructible. You will find this argument, sometimes more or less

disguised, in many philosophers. But the notion of substance, in

the sense of a permanent entity with changing states, is no longer

applicable to the world. It may happen, as with the electron, that a

string of events are so interconnected causally that it is practically

convenient to regard them as forming one entity, but where this happens

it is a scientific fact, not a metaphysical necessity. The whole

question of personal immortality, therefore lies outside philosophy,

and it is to be decided, if at all, either by science or by revealed

religion.

I will take up another matter in regard to which what I have said may

have been disappointing to some readers. It is sometimes thought that

philosophy ought to aim at encouraging a good life. Now, of course,

I admit that it should have this effect, but I do not admit that it

should have this as a conscious purpose. To begin with, when we embark

upon the study of philosophy we ought not to assume that we already

know for certain what the good life is; philosophy may conceivably

modify our views as to what is good, in which case it will seem to

the non-philosophical to have had a bad moral effect. That, however,

is a secondary point. The essential thing is that philosophy is part

of the pursuit of knowledge, and that we cannot limit this pursuit by

insisting that the knowledge obtained shall be such as we should have

thought edifying before we obtained it. I think it could be maintained

with truth that _all_ knowledge is edifying, provided we have a right

conception of edification. When this appears to be not the case it is

because we have moral standards based upon ignorance. It may happen by

good fortune that a moral standard based upon ignorance is right, but

if so knowledge will not destroy it; if knowledge can destroy it, it

must be wrong. The conscious purpose of philosophy, therefore, ought

to be solely to _understand_ the world as well as possible, not to

establish this or that proposition which is thought morally desirable.

Those who embark upon philosophy must be prepared to question all

their preconceptions, ethical as well as scientific; if they have a

determination never to surrender certain philosophic beliefs, they are

not in the frame of mind in which philosophy can be profitably pursued.

But although philosophy ought not to have a moral purpose, it ought

to have certain good moral effects. Any disinterested pursuit of

knowledge teaches us the limits of our power, which is salutary; at

the same time, in proportion as we succeed in achieving knowledge, it

teaches the limits of our impotence, which is equally desirable. And

philosophical knowledge, or rather philosophical thought, has certain

special merits not belonging in an equal degree to other intellectual

pursuits. By its generality it enables us to see human passions in

their just proportions, and to realise the absurdity of many quarrels

between individuals, classes, and nations. Philosophy comes as near

as possible for human beings to that large, impartial contemplation of

the universe as a whole which raises us for the moment above our purely

personal destiny. There is a certain asceticism of the intellect which

is good as a part of life, though it cannot be the whole so long as

we have to remain animals engaged in the struggle for existence. The

asceticism of the intellect requires that, while we are engaged in the

pursuit of knowledge, we shall repress all other desires for the sake

of the desire to know. While we are philosophising, the wish to prove

that the world is good, or that the dogmas of this or that sect are

true, must count as weaknesses of the flesh--they are temptations to

be thrust on one side. But we obtain in return something of the joy

which the mystic experiences in harmony with the will of God. This joy

philosophy can give, but only to those who are willing to follow it to

the end, through all its arduous uncertainties.

The world presented for our belief by a philosophy based upon modern

science is in many ways less alien to ourselves than the world of

matter as conceived in former centuries. The events that happen in

our minds are part of the course of nature, and we do not know that

the events which happen elsewhere are of a totally different kind.

The physical world, so far as science can show at present, is perhaps

less rigidly determined by causal laws than it was thought to be;

one might, more or less fancifully, attribute even to the atom a

kind of limited free will. There is no need to think of ourselves as

powerless and small in the grip of vast cosmic forces. All measurement

is conventional, and it would be possible to devise a perfectly

serviceable system of measurement according to which a man would be

larger than the sun. No doubt there are limits to our power, and it

is good that we should recognise the fact. But we cannot say what

the limits are, except in a quite abstract way, such as that we

cannot create energy. From the point of view of human life, it is

not important to be able to _create_ energy; what is important is to

be able to direct energy into this or that channel, and this can do

more and more as our knowledge of science increases. Since men first

began to think, the forces of nature have oppressed them; earthquakes,

floods, pestilences, and famines have filled them with terror. Now at

last, thanks to science, mankind is discovering how to avoid much of

the suffering that such events have hitherto entailed. The mood in

which, as it seems to me the modern man should face the universe is

one of quiet self-respect. The universe as known to science is not in

itself either friendly or hostile to man, but it can be made to act as

a friend if approached with patient knowledge. Where the universe is

concerned, knowledge is the one thing needful. Man, alone of living

things, has shown himself capable of the knowledge required to give

him a certain mastery over his environment. The dangers to man in the

future, or at least in any measurable future, come, not from nature,

but from man himself. Will he use his power wisely? Or will he turn

the energy liberated from the struggle with nature into struggles with

his fellow-men? History, science, and philosophy all make us aware

of the great collective achievements of mankind. It would be well if

every civilised human being had a sense of these achievements and a

realisation of the possibility of greater things to come, with the

indifference which must result as regards the petty squabbles upon

which the passions of individuals and nations are wastefully squandered.

Philosophy should make us know the ends of life, and the elements in

life that have value on their own account. However our freedom may

be limited in the causal sphere, we need admit no limitations to our

freedom in the sphere of values: what we judge good on its own account

we may continue to judge good, without regard to anything but our own

feeling. Philosophy cannot itself determine the ends of life, but it

can free us from the tyranny of prejudice and from distortions due

to a narrow view. Love, beauty, knowledge, and joy of life: these

things retain their lustre however wide our purview. And if philosophy

can help us to feel the value of these things, it will have played

its parts in man’s collective work of bringing light into a world of

darkness.

INDEX

Æther or empty space, 107

Analogy, positive and negative, 271

_Analysis of Sensations_ (Mach), 292

_Animal Intelligence_ (Thorndike), 30

Animal learning, study of, 29 ff.

Thorndike’s laws of, 31 f.

learned reactions, 35 f.

_A priori_, causation not regarded as, 150

knowledge, 249 f., 265

probability, on Keynes’s theory, is, 274

logic, 296

Aristotle, 226

Association, principle of, 33 f., 48, 64, 180

Aston, Dr. F. W., 99

Atom, theory of the, 98 ff.

centre from which radiations travel, 157

philosophical consequences of modern study of the, 293

Attention, 205

Bacon, 80

Behaviourism, its view of man, 70 ff.

where it breaks down as a final philosophy, 129

dilemma put to, 133

its propositions as to thought examined, 169 ff.

and logic, 263

_Behaviourism_ (Watson), 22, 31, 33

“Belief”, 254, 258 ff.

definition of, 261

Beliefs, defects in common, 3 ff.

Bergson, 71, 73, 198

Berkeley, 246 f.

_Bodily Changes in Pain, Hunger, Fear and Rage_ (Cannon), 218

Body, human, 25, 139

Bohr, Niels, his addition to the theory of atoms, 101 ff.

Bradley, monistic view of, 251

criticism of his argument against relations, 252

Braithwaite, R. B., 269

Brentano, 202

Broad, Dr., 188, 195, 282, 292

Buddha, 227

Butler, Samuel, 71

Cannon, 218

Cantor, Georg, 296

Casuistry, 225

Causation, as an _a priori_ belief, 5, 150

notion of “necessary” sequence, 115

conception of, in science, 144 ff.

“Cause”, Kant’s category of, 248 f.

“Chrono-geography”, 283

Cognition, 61, 202 f., 217

Conation, 202

Conception, 203

“Conditioned reflexes”, 35

Confucius, 227

Conscience, 228

“Consciousness”, 60

William James’s views on, 210

two different meanings of the word, 210

criticism of common sense view of, 211 ff.

self, 214

William James’s views approved, 217

one kind of mnemic effect, 288

Continuity in nature, 108

Correlation, laws of, 117

_Critique of Practical Reason_ (Kant), 249

Curiosity, 220

Dalton, 98

“Data”, 266 f., 276

De Broglie, 278

Decalogue, the, 227

Descartes, 9, 162 ff., 237 ff.

Desire, behaviourist view of, 90 f.

introspective view of, 221 ff.

Dewey, John, 292

Discontinuity in nature, 101, 106, 108

Dreams, 62, 127, 175, 176, 185, 189, 193

Dualism of mind and matter, 141, 239

Ductless glands, the, 218

Eddington, Professor, 273, 279

Education, 233

Einstein, 96, 116, 239, 242, 249

Electron, 99 ff., 118, 145

“Emergent” properties, 282

Emotions, essential physiological conditions of the, 118

subject to “Conditioning”, 119

generate irrational opinions, 120

Energy, radiation of, from matter into empty space, 145

propagation in empty space, 145

impact on matter in empty space, 146

_Essays in Radical Empiricism_ (William James), 210, 292

Ethics, views of the ancients on, 227

theory that virtue consists in obedience to authority, 227 ff.

utilitarian theory of, 229 f.

the concept of “good”, 230

mainly social, 233

the supreme moral rule, 234 f.

Events, in physics, 110 f.

string of, 118 f.

“mental”, 141, 280 ff.

structure and mathematical laws of, 157

minimal, 277

matter constructed out of, 278

Experience, effects of, in a reaction to stimulus, 180 ff.

Familiarity, a stage in memory, 195 f.

Fear and Rage, 219

Feeling, as mental occurrence, 202

Forces, 111, 114, 117, 120 f.

Form, reaction to, 85 f.

Freudian “unconscious” the, 221

Galileo, 80

Generalisations, 271 f.

Geodesic, 112, 117

Geometry, as empirical as geography, 249 f.

_Gestaltpsychologie_, 37, 41, 43, 68, 247

Gravitation, 116 f., 145, 279

Griffith, Mr. Percy, 118

Habit-formation, 36

Habit-memory, 188, 196

Hegel, 227, 229, 251

Heisenberg, 96, 105, 278, 293

Heisenberg-Schrödinger theories of atomic structure, 243

Heraclitus, 251

Huc, Monsieur, 232

Hume, 180, 191, 247 f.

Images, visual, auditory and tactual, 176

behaviourist explanation of, 177 f.

difference between sensations and, 179 ff.

definition of, 184 f.

first stage in memory, 195

Imagination, analysis of, 190 ff.

essence of, 191

exceptional gifts of, 193

and belief, 193 f.

difference between memory and, 194

Induction problem of validity of, 14

as a practice, 80 f.

principle of, 268 f.

logical problem of, 269 ff.

Mr. Keynes’s examination of, 270 ff.

Inference, “physiological”, 13, 80 ff., 135

syllogistic, 79

inductive and mathematical, 83 ff.

“Innate ideas”, doctrine of, 245

Interval, space-like and time-like, 110 f.

Introspection, 10, 11, 12, 172 f., 201 ff.

James, William, 210, 223.

Kant, 80, 201, 239, 248, 296

Keynes Mr., on problems of induction, 269 ff.

Köhler, 37 ff.

Knowing, as mental occurrence, 202

Knowledge, as displayed in reactions to environment, 17 ff.

perceptual, 58 ff.

behaviourist view of, 88 ff.

difference between introspective and other, 215

_a priori_, 249 f.

limitations on, imposed by structure of language, 264 f.

Knowledge-reaction, 216, 282

Language, as a bodily habit, 43 ff.

psychological side of, 48

words in an ideal logical, 256 f.

and things, relation between, 264

Laws, causal, 144 ff.

evidence for, 147

universal characteristics of, 149

Learning, laws of, 23, 29 ff.

two ways of, 39

in infants, 41, 48

by increase of sensitivity, 95 f.

Leibniz, 239, 241 f.

_Le Problème logique de l’induction_ (Jean Nicod), 269, 273

Locke, 244 ff.

Logic, 263, 296

“Logical atomism”, 248

Mach, 214, 292

Man, his relation to the Universe, 292, 295, 298 ff.

Materialism, as a philosophy, 159

_Mathematical Theory of Relativity_ (Eddington), 283

Matter, the structure of the atom, 98 ff.

essence of, 146 f.

as conceived in modern physics, 157, 293

old view of, now untenable, 158 ff.

constructed out of events, 278

permanence of, only approximate, 279

possibly a structure of mental units, 290

Maxwell’s equations, 107, 145

Meaning, 52, 71, 82

Meinong, 202

Memory, behaviourist theory of, 71 ff.

its reference to the past, 188 ff.

feeling of pastness complex, 190

more fundamental than imagination, 190

vital difference between imagination and, 194

Dr. Broad’s view on reference to the past, 195

stages of, 195 ff.

immediate, 196 f.

true recollection, 197 ff.

trustworthiness of, 199

Memory and testimony, 5 ff.

Mendeleev, 99

“Mental” events, 114, 141 f., 280 f.

“Mental” occurrences, 201, 212

_Mentality of Apes_ (Köhler), 37 ff., 62

Mill, J. S., his canons of induction, 269 f.

Mind and matter, conventional notions of, 141

distinction between, illusory, 142, 201

gap between, how filled in, 148

interaction between, 150

theory of “neutral monism”, 206 ff.

Cartesian dualism, 239

Leibniz’s theory of, 241

Mind, a cross-section in a stream of physical causation, 150

modern conception of, 280 ff.

emergent from events, 284

definitions of a, 285 ff.

Minkowski, 239

_Mneme_ (Semon), 49

“Mnemic” effects, 49, 209, 295

“Mnemic” occurrences, 49, 180 f.

Monads, 241

Monists and pluralists, controversy between, 251 ff.

pluralism the view of science and common sense, 253

Moore, Dr. G. E., on notion of “good”, 230

“Moral issues”, 227

Motion, 119, 163

Mystics, 229, 264, 300

Names, 53

Necessity, anthropomorphic notion of, 115, 117

“Neutral monism”, theory of, 206 ff., 210, 282, 292

Newton, 242

Nisbet, R. H., on probability, 275

Object, what happens when we see an, 146 f.

Objective and subjective study, 30

Objectivity, 154 f., 169

Ogden and Richards, Messrs., 52

Parmenides, monistic view complete in, 251

Parry, Professor R. B., 292

Perception, difference between introspection and, 10 f.

a species of sensitivity, 59, 123

and inference, 65 f.

from objective standpoint, 66 ff.

of external event, analysis of, 123 ff.

element of subjectivity in, 130 ff.

and causal laws of physics, 145 ff.

its relation to the object causal and mathematical, 149

from introspective standpoint, 201 ff.

Perceptive knowledge, stages in act of, 18 ff.

Percepts, 133, 135, 137 ff.

Perspective, 152

Philosophy, the business of, 2, 236

Behaviourism as a, 129 ff.

Utilitarian, 229 f.

systems of Descartes, Spinoza, and Leibniz, 237 ff.

Locke, Berkeley, and Hume, 244 ff.

conscious purpose of, 299

Physics, modern, 97

causal laws in, 114 ff., 145 ff.

and perception, 123 ff.

spatial relations in, 137 ff.

our knowledge of, 151 ff.

only mathematical properties of, discoverable, 157

less deterministic than formerly, 239

and psychology, 282, 289

Pictures, as representations, 183

“Planck’s Constant”, 101 f.

Plato, 226

Poetry, 220

Probability, fundamental in science, 274

_a priori_ on Mr. Keynes’s theory, 274

“frequency”, theory of, 274 f.

Psychology, 16, 172, 184

and physics, 282, 289

“Psychophysical parallelism”, 238

“Public good”, the, 230

Publicity, in the case of physical phenomena, 170

Quantum changes, 106

Radio-activity, 99, 103

Reactions, learned, 21, 33, 35, 36, 49, 81

Realism, naive, 175

Recognition, two forms of, 196

Recollection, true, 197 ff.

Relations, Bradley’s argument against, 252

cause of confusion about, 264

Relativity, theory of, “space-time” instead of one cosmic time and

space, 108

some results of the, 108 ff.

“events” instead of bodies moving, 110

relations between “events”, 110 f.

no “forces” in the, 111

philosophical consequences of the, 293

“Right conduct”, 230

Rutherford, Sir E., 99, 101

Santayana, Mr., 230

Schiller, Dr. F. C. S., 79

Schrödinger, 98, 105, 278, 293, 294

Self-observation, 126, 161 ff.

basis of Descartes’s system, 162 ff.

Dr. Watson’s views, 167 ff.

gives knowledge not part of physics, 175

Semon, 49, 180

Sensation, difference between images and, 179

acoleuthic, 197

as opposed to perception, 204

Sensitivity, 59 f., 88, 123, 177

Sentences, 51, 54, 75, 255, 264

Sequence, laws of, 116

Shakespeare, 192

Sheffer, Dr. H. M., 282, 292

Sight, compared with touch, 156 f.

Size, sense of, 153

Socrates, 226

“Solipsism”, 291

Sommerfeld, 103

Space, one persistent, abolished in relativity theory, 108

physical and perceptual, 137 ff., 241 f., 294

Space-time, in theory of relativity, 108 ff.

structure of, 145

point-instant in, 278

“Specious present”, 195, 197

Spinoza, 238, 251

_Stars and Atoms_ (Eddington), 279

“Statement”, definition of a, 260

Subjectivity, 129, 133, 135, 154 f.

Substance, 5, 242 ff., 293

Syllogism, the, 80

Syntax, influence of, on philosophy, 243

connection between laws of physics and laws of, 263

Talking without thinking, 190

Tendency, quantitative laws of, 144

Testimony, 11 f., 170

_The Analysis of Matter_ (Bertrand Russell), 278

_The Meaning of Meaning_ (Ogden and Richards), 52

_The Mind and Its Place in Nature_ (Dr. Broad), 76, 188, 282

Thorndike’s “provisional laws”, 31 ff.

Thought, 163 ff., 174, 240, 263

Time, not cosmic, 108 ff., 158

Touch, compared with sight, 156

_Treatise on Probability_ (Keynes), 269 ff.

Truth, 94, 261 f.

Truth and Falsehood, causes of mystery about, 254

two questions in, 254 ff.

meaning of a sentence examined, 255 f.

grounds on which statements are regarded as true or false, 257

ultimate test of falsehood, 258

“belief”, 258 ff.

problems of, 259 ff.

Universals, 53, 203

Universe, the, philosophy concerned with, 236

man’s relation to, 298 ff.

“Unlearned Equipment”, 22

Utilitarian philosophy, 229 f.

Vitalists, 25

Volition, 61

Watson, Dr. J. B., 10, 21, 22, 31, 33, 35, 36, 37, 70 ff., 126 ff.,

162, 167 ff., 177, 188, 219, 223, 259

Waves in empty space, 107 f.

Whitehead, Dr., 159

“Will”, 223 f.

Willing, as mental occurrence, 202

_Winds of Doctrine_ (Santayana), 230

Wish-fulfilment and dread-fulfilment, 194

Wittgenstein, 264

Words, purpose of, 11 f.

as physical occurrences, 44 ff.

spoken and written, 46 f.

how acquired by infants, 48 ff.

meaning of, 52, 256

relations of, 56

in an ideal logical language, 256 f.

World, the physical, nature of our

knowledge of, 151 ff.

a four-dimensional continuum of events, 293

our knowledge of, purely abstract, 295

THE END

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Transcriber’s Notes

Hyphenation, and spelling were made consistent when a predominant

preference was found in the original book; otherwise they were not

changed.

Original text mostly placed commas and periods after closing quotation

marks, but occasionally placed them before closing quotation marks.

This inconsistency has not been changed here.

Simple typographical errors were corrected; unbalanced quotation

marks were remedied when the change was obvious, and otherwise left

unbalanced.

Footnotes have been sequentially renumbered and placed just below

the paragraphs that reference them.

The index was not checked for proper alphabetization or correct page

references.

Page 86: The variables in the equation were printed in italics. To

improve readability, the underscore characters used elsewhere to

indicate italics have been omitted in this case.

Page 207: “this is a causal word” originally was printed as “this a a

causal word”; changed here by Transcriber.