Space, Time and Deity
3: The Order and Problems of Empirical Existence
Chapter 1: The Clue to Quality
Samuel Alexander
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A. MIND AND ITS NEURAL BASIS
Introductory
EMPIRICAL things are complexes of space-time with their qualities ; and it is now my duty to attempt to show how the different orders of empirical existence are related to each other, and in particular to explain more precisely the nature of qualities which hitherto have merely been described as being correlative with their underlying motions, the exact nature of this relation having been left over for further consideration. To do this is the second and perhaps the more difficult of the two problems assigned to metaphysics in the Introduction. The first was to describe the fundamental or a priori elements of experience. The second was to explain what empirical existence is and to indicate those relations among empirical existences which arise out of the a priori features of all existence, if any such can be discovered. In making this attempt I am met by a particular difficulty. My principal object is to ask whether minds do not fall into their appropriate place in the scale of empirical existence, and to establish that they do. It would be most convincing if minds were first mentioned in their place at the end of the scale. But this procedure would compel me to use conceptions which would remain difficult until their application to minds was reached. Moreover, the nature of mind and its relation to body is a simpler problem in itself than the relation of lower qualities of existence to their inferior basis ; and for myself it has afforded the clue to the interpretation of the lower levels of existence.
(4) I shall therefore adopt a method of exposition (not of demonstration) which partakes of compromise, and shall preface the inquiry with two problems as to mind, the solution of which can be used as a clue and a means of simplification. The one problem is the relation of mind to the living organism with which, or with a part of which, it is correlated. The other is the relation of minds to one another. I shall then be able to state a hypothesis as to Space-Time and the kinds of empirical existence,—matter, life, mind, to name the most obvious distinctions, —which arise within the one Space-Time.
Identity of mental with its neural process.
Mind is at once the case which most urgently forces on our attention the problem of quality and at the same time offers the readiest means for its solution. For our mind is experienced by us as a set of connected processes which have the character of being mental, possessing the quality of mentality,' or as I shall most frequently say, the character of consciousness. Whether there is any department of mind, which, remaining mind, may be said to be unconscious, and in what sense this is true, is a question I shall defer for the present. Any one who wishes can substitute for the quality of consciousness the quality of being mind, and can, if he pleases, continue to think of mentality as something less specified than consciousness. A mind, then, is for immediate experience a thing or organisation of processes with this distinctive property of being mind, and, however much interrupted it may be, it is normally linked up by memory in its various forms. Under consciousness I include without further ado those vague and indistinct mental processes on the extreme margin of consciousness which are sometimes described as subconscious, such as, in general, the tone of the organic sensations when we are occupied with external events. Such then is mind as we experience it. But we experience also our bodies, and, moreover, in the organic and motor sensations, such as hunger and breathing and the like, we experience our bodies as alive, while they are also experienced by touch and sight, etc., as being physical things of the order of external things. And, as
(5) we have seen in a previous chapter, experience leads us on to connect our mental processes with our body, and in particular with our central nervous system, and more specifically still with a certain part of our brain, and to localise our mental processes in the same places and times [1] as certain neural processes. We thus become aware, partly by experience, partly by reflection, that a process with the distinctive quality of mind or consciousness is in the same place and time with a neural process, that is, with a highly differentiated and complex process of our living body. We are forced, therefore, to go beyond the mere correlation of the mental with these neural processes and to identify them. There is but one process which, being of a specific complexity, has the quality of consciousness ; the term complexity being used to include not merely complexity in structure or constitution of the various motions engaged, but also intensity, and above all unimpeded outlet, that is, connection with the other processes or structures with which the process in question is organised. For failure in intensity may mean failure of an otherwise sufficiently complex process to be conscious, and so may any cause which disconnects it from the rest of the neural processes which in their connection give us mind. Correlation is therefore an inadequate and misleading word to describe the relation of the mental to the corresponding neural process, and is only used provisionally so long as the two are separated from one another. In truth, according to our conception, they are not two but one. That which as experienced from the inside or enjoyed is a conscious process, is as experienced from the outside or contemplated a neural one. When we speak of them separately it is that we consider the same process first in respect of the character which allies it with simpler vital processes, and second in respect of the new quality which emerges at this higher stage of vital complexity. It has then to be accepted as an empirical fact that a neural process of a certain level of development possesses the quality of consciousness and is thereby a mental process ; and,
(6)alternately, a mental process is also a vital one of a certain order.
Consciousness something new in life.
Now it is not the character of being vital that gives the mental process
its individuality, but its new quality of mentality or consciousness.
Let us take as examples of vitality such operations as digestion or
breathing or secretion. There is no reason that I know for not reckoning
with them physiological reflex action or any neural process not attended
with consciousness or mind. But while mental process is also neural, it
is not merely neural, and therefore also not merely vital. For, that
mind should emerge, there is required a constellation of neural or other
vital conditions not found in vital actions which are not mental. To use
the word which Mill has made familiar, mind requires, as a fact of
experience, a collocation of conditions which constitutes something new.
What that collocation is, might be very difficult for any one but a
physiologist to say, and perhaps not possible completely for him. I take
it that in the main what determines the difference of the psychical from
the merely physiological process is its locality in the nervous system,
implying as this does the special structure of the living nervous
elements in that locality. It may still be open for discussion at what
level in the brain-structure consciousness is found, whether it may
attend processes in some of the higher ganglia or whether it belongs
exclusively to the cerebral cortex, or whether, again, it is not
different if it belongs to a lower and a higher level in the cortex
itself. But assuming that the conception of localisation of mental
functions in specific regions of the brain is physiologically correct,[2]
we may safely regard locality of the mental process as what chiefly
makes it mental as distinct from merely neural, or what distinguishes
the different sorts of mental processes from one another. This is,
however, a subsidiary matter for our purposes.
(7) What counts is, that without the specific physiological or vital constellation there is no mind. All less complex vital constellations remain purely vital. Thus not all vital processes are mental. There is not, or not necessarily, to each neurosis a corresponding psychosis. The equivalent proposition is, that while all psychoses are neuroses, the psychoses imply the emergence of a new feature, that of mind. It would follow that mental process may be expressible completely in physiological terms but is not merely physiological but also mental. Its resolution into physiological terms may be infinitely difficult, and even if it can be performed it remains that the statement of these conditions only means mental action because we are already acquainted with the fact of their mentality. To put the matter in different terms : suppose we regard the description of mind as a chapter of physiology ; it would still be the physiology of mental action ; we should still be attending to this kind of physiological constellation because it is the basis of mind, and should be directed to it from psychology. Nor, as we shall see later, could any physiological knowledge of the physiological constellation implied in a mental action enable us to predict that it would have the mental quality.
Mental process is therefore something new, a fresh creation, which, despite the possibility of resolving it into physiological terms, means the presence of so specific a physiological constitution as to separate it from simpler vital processes. I do not mean, to take a particular and interesting case, that the foresight of ends as distinguished from mere vital purposiveness, is not also vital. Every idea of an end to be gained, every thought of a universal, or of a combination to be made executive by some invention, I shall assume to be also a physiological process. I mean that such processes though they may be reduced to the class of vital processes are so distinct from the remainder of the class that they hold a privileged position in it. Precisely in the same way the king is a man and belongs to the same class with his subjects. But he is not one of his subjects. Abt Vogler in Browning's poem declares of the musician
(8) " that out of three sounds he frames not a fourth sound but a star." Out of certain physiological conditions nature has framed a new quality mind, which is therefore not itself physiological though it lives and moves and has its being in physiological conditions. Hence it is that there can be and is an independent science of psychology, and that the translation of mental processes into their physiological counterparts follows the lead of the more primary description of mind. Mind is thus at once new and old. No physiological constellation explains for us why it should be mind. But at the same time, being thus new, mind is through its physiological character continuous with the neural processes which are not mental. It is not something distinct and broken off from them, but it has its roots or foundations in all the rest of the nervous system. It is in this sense that mind and mental process are vital but not merely vital.
Consciousness not an epiphenomenon
Hence it follows that we are entitled summarily to dismiss the conception that mind is but an inert accompaniment of neural process, a kind of aura which surrounds that process but plays no effective part of its own : the doctrine that mind is an epiphenomenon of nervous process, which nervous process would continue to work equally well if mind were absent. The doctrine is not simply to be rejected because it supposes something to exist in nature which has nothing to do, no purpose to serve, a species of noblesse which depends on the work of its inferiors, but is kept for show and might as well, and undoubtedly would in time be abolished. It is to be rejected because it is false to empirical facts. The mental state is the epiphenomenon of the neural process. But of what neural process ? Of its own neural process. But that process possesses the mental character, and there is no evidence to show that it would possess its specific neural character if it were not also mental. On the contrary, we find that neural processes which are not mental are not of the same neural order as those which are. A neural process does not cease to be mental and remain in all respects the same neural
(9) process as before. Even if it remains in the same place, its connection with the rest of the brain is in some way disturbed, and it cannot proceed freely on its course. The neural process which carries thought becomes changed into a different one when it ceases to carry thought. All the available evidence of fact leads to the conclusion that the mental element is essential to the neural process which it is said to accompany by way of embellishment, and is not accidental to it, nor it in turn indifferent to the mental feature. Epiphenomenalism is a mere fallacy of observation.[3]
No parallelism of neural and mental processes.
It is otherwise with the other well-known doctrines of the relation of body and mind. The statement which has been given above is by no means new in principle nor for that matter in its particular form. It is a species of the identity doctrine of mind and body, maintaining that there are not two processes, one neural, the other mental, but one. We shall do well to deal shortly with these other doctrines, not in order to treat the subject with thoroughness but to defend it sufficiently for our objects against the rival conceptions, or at least to exhibit the contrast between it and these conceptions.
The mental process and its neural process are one and the same existence, not two existences. As mental, it is in my language enjoyed by the experient ; as neural it is contemplated by an outsider or may be contemplated in thought by the experient himself. There can therefore be no parallelism between the series of mental and the series of neural or physiological events, such as is postulated by the strict theory of so-called psychophysical parallelism. That theory was devised to give expression to the complete disparity of the merely physiological and the mental, and the reason for it disappears so soon as it is
(10) recognised that what corresponds to the mental is not merely physiological but the bearer of a new quality. It solved or evaded the problem by regarding the mental series as entirely independent of the neural and yet in precise correspondence therewith. The difficulties of establishing such precise correspondence in detail may be neglected here, and they are probably not insuperable. But it is evident (as Mr. 'Ward convincingly pointed out [4]) that an exact correspondence of two completely disconnected series, which do not influence each other, is no more than a restatement of the problem. The only solution it offers is that the problem must be left unsolved. It could therefore at most be accepted for psychological purposes as a compendious statement of the fact that every psychosis has its corresponding neurosis. There still remains the metaphysical question whether the mind whose processes are mental is not a being which interacts with the brain, or whether, as I have urged, the mind is not itself identical with the totality of certain neural processes as they are enjoyed.
But even as a psychological convenience, the theory is without
justification and superfluous, and moreover false in what it suggests.
Psychology is concerned with a parallelism between the mental series and
another series of a different order, the series of physical objects of
which the mental processes are aware. One of the drawbacks of the order
of exposition I am adopting is that I must take for granted what will
only be fully clear hereafter (though it has been formulated
provisionally in the Introduction), that the object of the mind in any
mental process is something non-mental, which is contemplated, while the
mental process is enjoyed. To each non-mental object (and there is no
mental process which is without its non-mental object, even if it be
only a sensum which is the object of sensing, even if it be only the
internal condition of the percipient's body as in organic sensation)
there corresponds a mental process which has the quality of conscious
awareness. As the
(11) object varies, so does the neural process or the mental process vary. But there is no parallelism of the neural and the mental series of which psychology should take account. They are one. Psychology considers the series from the point of view of the experient or enjoyer ; physiology from the point of view of the onlooker, or, if of the experient himself, not in his character of experiencing the mental process but of reflecting on its basis in neural process.
I can only account for the admission of a metaphysical miracle as a convenient psychological fiction by supposing that mental processes were believed to have not merely the quality of consciousness, but other qualities disguised under the name of 'content' which varied with the object. If the sensory object blue or the image of a table is in some way contained in the apprehension of it, doubtless there is an unbridged chasm between the neural process which clearly has no such content' and the mental process which has. No one has indeed imagined that a mental process was itself blue or tabular. Yet these processes are supposed to be qualified correspondingly, or at least to have before them presentations or ideas which are not themselves merely external or a selection from what is external. The lingering tradition of representationism provides a mental process (hence called a mental state) with a mental object. But once we recognise that mental processes have no character, beyond the quality of being mental, other than such as all processes present, intensity or locality or velocity and the like, that is to say, empirical forms of categorial characters, all reason is removed for supposing the mental process to be a different existent from the neural one. That neural process differs with every difference in the object which stimulates it to activity, or upon which it is directed. The neurosis of green occurs for instance in a different place from that of sweet. The neuroses all possess the vital quality but are different configurations of categorial characters. In like manner the psychoses present, corresponding to the qualities of the object, differences in the process-features of the psychosis ; but there is nothing to indicate the
(12) difference of quality of the object but these process-features. The separation of the mental process from the neural one is therefore superfluous, for it is the same process-features which are in the one case enjoyed and in the other contemplated. Ultimately this separation depends upon failing to recognise the distinctness of the mental process from its non-mental object. It is therefore not only superfluous but founded in error.
Causality between mind and brain
If we do not regard the mind as the connected totality of its mental processes and therefore identical with the totality of the physiological processes of which they are the presence in enjoyment, the only alternative is some form of animism ; which conceives the mind as an independent entity which acts upon, or is acted upon by, the brain, or operates through it as the instrument of mind. On our view it still remains true that mind and brain interact if the phrase is properly interpreted. Just as we continue to speak of sunrise and sunset, though it is the earth that revolves, so we may continue to say under a certain proviso that the mind, as in an act of will, acts upon the brain directly and produces indirectly movements of the limbs ; or that a stimulus excites the mind through the brain and sets going a train of thought. The proviso under which such language is permissible is that no brain process shall be understood to cause its corresponding mental process and no mental process its corresponding brain process. Let large letters denote the psychical and small ones the neural series. What we have then in fact is a series, Aa, Bb, Cc, etc., where some of the small letters may have no corresponding large letter at all. Now A does not cause a but is identical with it ; but A being also a may cause the next member of the series b, and if b is equivalent to B, A causes also B. Strictly speaking, the effect of A is B and of a, b. But in so far as A does not exist without a, A also causes b. And where some of the steps in the causal chain as in willing are purely neural, A causes them because it is itself a neural process a. In like manner no sensory neural process a causes the corresponding sensing A, for it actually is that process ; but in
(13) so far as it is identical with A it may be said to cause the next psychical event B. In this way we may legitimately say that my determination to strike a man causes the blow of my fist ; or that a piece of yellow makes me think of an orange tree in a garden on the Palatine Hill. Just because mind is also vital it can act on my body, and because some neural results of stimulation are also mental, my brain may act upon my mind. There is therefore causality between the members of the mental series and between those of the physical series, and because of the identity of the mental with its physical correspondent there is causality in the sense defined between members of the two series.
Animism
Needless to say, it is not such interaction of mind with brain which is implied in the notion of animism. The mind is there distinct from the neural series. But the reasons which have been thought more recently to compel the adoption of animism have, more particularly in the impressive statement of Mr. McDougall,[5] been coloured by antagonism to the notion of psychophysical parallelism. The argument has also assumed, or seemed to assume, the alternative to animism to be the so-called associationist conception of mind, according to which mind consists of a number of separate events corresponding to separate objects linked together by associative connections. There are sensations or ideas grouped together into wholes by contiguity or similarity. To this correspond on the neural side certain central excitements which are connected by association-fibres. This crude psychology, obsolescent in this country since the article 'Psychology' of the ninth edition of the Encyclopedia Britannica, may fairly be regarded now as obsolete. Mental processes are not grouped into wholes by association but are distinguishable processes within a mental continuum. The agglutinative conception of mind is replaced by the organic one. Mind has its structure and constitution as an animal body has. Moreover, as we have seen, the life of mind is essentially one of
(14) transition, and substantive processes of mind like perceptions or images are but the more stable processes corresponding to things in the object world which stand out in the stream, while the transitive ones are the vaguer, but still definite processes, which correspond to the relations among the objects. Now, when the notion of psychophysical parallelism is rejected in its natural form and the assumptions of associationism are dismissed, the arguments in favour of animism lose half their persuasiveness. It will be as well to substantiate this proposition by indicating the considerations which on our hypothesis of identity modify these arguments. I am able to be shorter on this subject because much of what I have to say has been already said by Mr.. Lloyd Morgan in the concluding chapter of his work on Instinct and Experience.[6]
The argument is that mind has certain specific characters to which there is or even can be no neural counterpart. It is not enough to say that there is no mechanical counterpart, for the neural structure is not mechanical but physiological and has life. Mind is, according to our interpretation of the facts, an 'emergent '[7] from life, and life an emergent from a lower physico-chemical level of existence. It may well be that, as some think, life itself implies some independent entity and is indeed only mind in a lower form. But this is a different question, which does not concern us yet. If life is mind, and is a nonphysical entity, arguments derived from the conscious features of mind are at best only corroborative, and it is an inconvenience in these discussions that the two sets of arguments are sometimes combined. Accordingly I may neglect such considerations as the selectiveness of mind which it shares with all vital structures. These considerations really obscure the issue. For even if life is an entity of a different order from existences on the
(15) purely physical level, it would still be a question whether mind is not so distinct from life as to claim to be a yet higher order of existence. Let us then confine ourselves at present to mind in its character of a conscious being. The important question is whether it must be conceived as discontinuous with the neural structure or (it the phrase be preferred) the neural mechanism.
(1) The argument from meaning.
'Meaning,' it is said, has no neural counterpart, but the use of meaning is the very life-blood of mind. Now it is important here to distinguish two senses of meaning, because the argument for animism has been used by different writers in the two senses. I may mean in the first place an object, as when I point with my finger to a person and say, I mean you. Meaning here signifies reference to an object, and in this sense every conscious process means or refers to an object other than the mental process itself. All mental action implies the relation of a subject to an object ; and it makes no difference whether the object is a perceived one present to the senses ; or an ideal one like a purpose consciously entertained, such as going to London as entertained in idea or in thought ; or even an imaginary object such as √-1. What neural (or as it is sometimes irrelevantly asked what mechanical) equivalent can there be for this unique relation ? This sense of meaning corresponds to what the logicians call the meaning of a word in extension. On the other hand, meaning may signify what the logician calls intension ; a word is used with a meaning ; a flower may mean for me a person who is fond of it ; " there's pansies, that's for thoughts " ; and in general our minds may have a sensory object before them, but what we mean by it is a thought which has no sensory embodiment. In the words, " when I say religion, I mean the religion of the Church of England as by law established," these two senses of the word meaning seem to be combined, but on the whole it is mainly in the second sense that the word is used.
Now meaning in extension raises a quite different problem from meaning in intension ; and that problem is not the question of the relation of mind to its alleged neural basis. It is the question whether the relation of
(16) the conscious subject to an object which transcends it is unique, or whether it is not, as I shall maintain, found wherever two finites are compresent with each other. It is the problem of what is involved in the knowledge of what is not-mental. To be conscious of an object, to mean it, or to refer to it, may turn out in the end to he nothing but the fact that, to take a particular case, a table excites in my mind a conscious process of perceiving it. Accordingly in this sense of meaning, meaning does not belong here but to a later stage of our inquiry. Nor do I think that it would have seemed relevant were not the neural structure taken as alleged to be mechanical. For if it is a vital structure there is surely nothing very farfetched in thinking that the stomata of leaves mean something beyond themselves, the air, to which they are adapted. I may then neglect meaning in the extensive sense for the present. (See later, pp. 89 ff.)
The other sense of meaning is undoubtedly relevant, and it offers real difficulty. For meaning is a conscious condition of mind. When I use a word, the meaning is in my mind (and of course besides this refers to something not in my mind). What then is meaning ? Any part of a complex whole means for me the rest of the complex. A word, for instance, has been intimately connected with the characters of the things it names, and it means those characters. That is what it is to use a word with a meaning. My perception of the word means my thought of what the word stands for. The sight of the orange means for me the feel of it ; the sight of the marble means its coldness. The knight on the chess-board means the moves which I may make with that piece. The symbol √-1 means its mathematical interpretation. Now what is there in meaning so described which prevents us from believing that the conscious meaning corresponds to or, as I should say, is identical with a certain neural process ? Doubtless if we imagine that our mind is made up of sensations connected together by mere indifferent lines of association, the solution is impossible. But if mental life is mental processes arranged in various complicated patterns, why should not a word set going in my brain,
(17) and also in my mind, that pattern of process which we call the meaning ? I have answered the question in anticipation when I pointed to the existence of imageless thought, customs of mind which may also be customs in the neural structure, not mere neural statical dispositions, but those neural exercises of a habit which are identical with the consciousness of a thought without its necessary embodiment in sense. When the exercise of the habit is more specific and detailed we may have the meaning turn into an illustration or concrete embodiment of the meaning, as when the word horse not only makes me think of horse but of the particular foal whose affection I attach to myself in the country by the offer of sugar. And when the marble looks cold the very essence of the condition of my mind is that the sight process is qualified by the ideal touch process, and the transition from the one to the other is in my mind. Even bare association of the orange with Sicily is more than the fact that I think of Sicily when I see an orange. Orange and Sicily are woven into a complex, of comparatively loose texture indeed as compared with the relation of cold to white in the marble, but still a texture in which the transition from the orange to Sicily is felt as a transition, and not as a mere juxtaposition. When I use a word like 'government,' a whole complicated neuro-psychical pattern is set going in my mind and brain, which is transitive and elusive, but none the less conscious, and only called transitive because it is wanting in definite detail. I may go on to fill out this transitive outline with the pictures of the coalition ministry. But it is still the elusive complex which stands out as the main occupation of my mind. The figures of the ministers are the fringes of it, not it the fringe of them. Thus mental connections to which correspond neural connections are as much conscious as what they connect, and meaning remains a unitary whole, while it still possesses its neural counterpart.
If meaning is thus neural as well as mental, it follows that a very slight change in an object, or stimulus, may produce an overwhelming difference in the mental response if that change is charged with meaning. The
(18) famous telegram argument for animism loses therefore all its force. A telegram 'our son is dead ' may find the recipient sympathetic but calm. Alter the word our ' to your,' a trifling change in the stimulus, and the recipient may be overcome with grief. On the other hand, change all the words into French, a large change in the stimulus, and the effect on the recipient is the same as when the telegram was in English. The facts present no difficulty in view of the constitution of the recipient's mind. The little change of a letter makes an enormous change in the meaning of the telegram. But the words mean the same in French as in English. No conclusion in favour of a mind independent of the neural process can be drawn unless we are prepared to say that a spark should physically produce the same effect when it falls on a sheet of iron as when it falls upon a mass of gunpowder, or that a red ball will not cause the same bruise when it hits my body as if it were painted white.
(2) The argument from fusion
Very different and far weightier are the considerations drawn from the phenomena of so-called fusion, that is to say where two stimuli which would singly produce their corresponding sensations produce, when acting together, a sensation different from either. It is thought that where this occurs there must somewhere in the neural mechanism be compounding of the physical effects : that there can be no compounding of mental states.[8] But in some cases at any rate there is said to be no such physical arrangement forthcoming. The subject is a technical one, and I cannot hope, nor am I fully able, to discuss it as it deserves. I desire only to remove a prejudice. It will be best to take a single case, that of so-called binocular fusion. Let the two eyes look at a disc or spot of light, the one eye through a blue the other through a red glass. Sometimes we see a disc of purple, but sometimes we see alternately either blue alone or red alone, in virtue of retinal competition. The possibility of this competition is taken to mean that the two stimuli are conveyed to different
(19) places in the brain
and do not compound their effects physically. And yet in spite of this
we can see purple on occasion. There is thus an action of the mind in
the sensation of purple which has no correspondent in the brain. There
is unity in the consciousness without unity in the cerebral neural
structure which carries the separate sensations. Many other such facts
are described by Mr. McDougall in his chapter on the unity of
consciousness, in particular those of 'binocular flicker.'[9] Mr.
Sherrington sums up his account of his experiments on this subject in
the striking sentence : " Pure conjunction in time without necessarily
cerebral conjunction in space lies at the root of the solution of the
problem of the unity of mind." [10]
Now I confess that if a mental state is also neural in the sense I have
assumed, it is difficult to understand how the mental states
corresponding to the two stimuli can affect each other if there is not
physical connection between them somewhere. But in the first place
inhibition between them, as in competition, seems to require some
communication between the neural processes which the stimuli set up. In
the next place, though there may be no connection between the sensory
centres of the two eyes yet the efferent process from each eye is
determined from both, as is indicated by the motor reactions of the two
eyes.[11] Mr. McDougall adds that
(20) the sensations are localised in the same external place and connects the " identical motor tendencies " of corresponding points with Lotze's doctrine that " local signature of the visual sensation is bound up with, or is a function of, the motor tendency excited by stimulation of that point.[12] Whatever value may attach to Lotze's doctrine, it is at any rate of the greatest importance to note that the sensations in question belong to ( 'are referred to ' or 'projected to,' are the ordinary, very questionable, phrases) the same external place. Now as long as there is physical connection somewhere, it is not necessary that the connection should be sensory or cerebral and be a conscious one as it is in the associative connections which were mentioned above. The significance of this will be apparent presently when we come to speak of the unity of consciousness.
Even then, it will be asked, how in the absence of composition of the two processes can there be a fusion of the two colours into a new colour purple ? Must this not at least be attributed to the mind apart from its cerebral instrument ? The question seems to presume the same misconception (or at least the same contradiction of my conception) which, as I have suggested, leads to the notion of a complete separation, of mere parallelism, of the psychical and the neural series. The assumption seems to be that the two mental processes, sensing blue and red, have blue and red for their content' or are qualified by those colours ; and in that case it is impossible to understand how the mental sensation of purple with its different content could arise in the absence of some new neural process resulting from the separate neural processes of blue and red. No wonder the fusion is then attributed to the mind itself. But if mental process is without quality or content save the quality of consciousness and corresponds to its object blue, or red, or what not, in virtue of its locality or the other spatio-temporal characters mentioned before, a different answer is possible and intelligible without difficulty.
(21) Granted the union somewhere of the neural processes of blue and red, even if the union be only at a common efferent path, we should say that these neural arrangements were the neural arrangements, carrying consciousness, which are correlated with the object purple, and that under these circumstances we were conscious of purple. There is no common sensory centre, let us admit, for the different excitements of the corresponding points in the two eyes. This is the arrangement, neural or mental, for seeing purple, when the purple is seen by both eyes in the same place.[13] There is another neural arrangement, in that case, for seeing purple when both red and blue stimulate the one eye alone. Yet there is no occasion to postulate an interfering soul. The alternatives are not between having a common centre for the two eyes, and assuming something which combines the two sensations into a different one. Both alternatives presuppose subtly that the quality of sensations belongs to the mind and a different one if not produced by external action in a brain centre must be manufactured by the mind. But there is a third alternative.[14] If we distinguish the sensing from the sensum, and hold that the sensum is in the external thing, then all our business is to note the difference in the neural machinery of response (carrying with it the quality not of the sensum but of consciousness) in the binocular instance. The brain centres being through the binocular arrangement affected neurally in the manner appropriate to purple, the mind sees purple. The " specific synergy," to use a phrase of Prof. C. Stumpf, is supplied neurally, though not by direct sensory connection, and the mind sees the object to which that specific synergy is the appropriately corresponding neural arrangement. What would need explanation is not so much why the
(22) mind sees purple under such conditions, but rather why under certain other conditions it sees only either one or other of the component colours. From this point of view there seems to me to be, in a sense not perhaps the same as his, a profound importance in the sentence I have quoted from Mr. Sherrington above. Two simultaneous processes in the mind, not necessarily connected at the conscious level, may form a single act of consciousness with an object different from that of either of the two mental processes taken singly.
The case of binocular flicker is a different one from the seeing of purple. The physical object is an intermittent illumination. The question is when the mind fails to detect the intermittence ; and it appears that in general the result is the same whether the stimulation is binocular or monocular. From Mr. Sherrington's experiments it appears that there is a difference when the rate of intermittence is different in the two sets of stimulations ; but here the objective difference of the sensa affects the sensibility for detection of intermittence. In these experiments also the sensations belong to the same place, and this is intimately connected with the common issue of the reaction from the visual centres.
Unity of consciousnees
This leads us directly to the problem of the unity of consciousness : how there can be such unity if the neural counterparts of the mental processes are not, as it is fairly clear is not always the case, united by connecting processes at the level of consciousness. This is one of two problems upon which our statement of the facts may perhaps throw light. The other problem is that of rupture of the unity of consciousness in spite of the existence of neural paths at the conscious level. If, as I have suggested, mental process is also neural there is no discontinuity (I mean disconnection) between those neural processes and processes occurring at lower levels of the nervous system or even of the organism taken as a whole. A conscious neural process may consequently be replaced (I purposely use a vague word to cover all cases) by a lower neural process which is not attended by conscious-
(23) ness. Nor is it enough to urge that possibly there may be discontinuity in the neural structure itself, for at the bottom of this neural structure there lies, as at the bottom of all finite existences, the indefeasible continuity of its space-time ; and the problem is but deferred to an earlier stage in the history of things.
Let us consider first the unity of consciousness. The case of fusion just discussed is enough to show that there may be unity of mind though the component processes are not connected at the conscious level. A still more obvious case is the unity of two experiences which do not fuse and are entirely disparate, such as a vision of trees and the touch of the chair on which I sit. These are disconnected experiences, but they are felt to belong to the one mind. Yet their nervous counterparts, though united by no definite neural connection at the conscious level, so long as they are not noticed to occur together, are part of one neural structure and are physically not disconnected at some level or other. Though these are united in time they are also connected somewhere in the neural space. Similarly there are gaps in time as that of dreamless sleep, where there is no consciousness in the ordinary interpretation of that word,[15] but where through some form of memory the interrupted history of our minds is united across the void. Our memory does not fill up this void but unites, to borrow the phrase once more, the broken edges of our mental life on the two sides of the gap. Thus the problem of mental unity assumes a different character. It is not how there can be mental unity without complete physical unification by lines of conscious connection, but how there can be unity in enjoyment when enjoyments are discontinuous though the neural structure as a whole is continuous. There is enough and to spare somewhere in the neural structure, to provide for everything in the mental life. The puzzle arises from the fact that while all psychoses are neuroses not all neuroses are psychoses. Hume, as I have so often pointed out, used the fact that the intermediate stages of
(24) a volition are not conscious but purely neural to controvert the notion that causality is a mental experience. We have, in other words, to account not so much for the apparent absence of neural connections as for the presence of mental unity though there are neural connections, but not direct mental ones. The fact of mental unity is beyond dispute. Our minds are normally unitary, and no matter how disconnected our experiences may be they are not experienced as merely juxtaposed to make a unity, but as differentiations of that unity. This is the initial and central fact of our mental life expressed by the somewhat loose phrase that the mind is sensibly or to experience continuous.
Now it is just because the neural structure is (at least relatively) continuous, so that all its parts are physically connected, that there can be unity between divided processes of consciousness, so as to make them belong to one mind. In other words, because conscious processes are parts of a larger whole which is not all of it conscious, in spite of the absence of conscious connections there is still connection.[16] This would be sufficient for our purposes, for it turns the flank of the contrary plea that for want of evidence of conscious connection we must assume an independent mind. Still the problem remains of how to understand the fact of experienced mental unity. Unity of substance, we have seen, means belonging to one contour of space-time. The unity of mind should be the unity of one enjoyed space-time. Yet though the mind is aware of its past stages as connected with the present ones, and though at any moment its various experiences belong to the one enjoyed space of the mind, there are gaps in time and gaps in space as it enjoys them, and we know, moreover, that there are such gaps. There are not gaps,
(25)as we have seen, in the physical basis taken as part of a larger neural structure. How then are we aware of these gaps in our enjoyment, and so enjoy our mental unity ?
The answer cannot be given till we come to learn how Space and Time themselves are apprehended. Various experiences palliate the difficulty but do not remove it. Sometimes we can by memory fill up the intervening time, going over the events between now and an hour ago. We cannot always do so, and never for the interval filled by dreamless sleep. Nor if we could, would the intervals of our memories be completely filled. From the reports of others we learn (as Leibniz observes) that we have continued to exist in sleep and can think of ourselves as existing in the interval, because we in turn have observed others to live in sleep, while from their reports they have not been conscious of the interval. Such experiences supplement but do not provide the direct consciousness we have of a mental unity containing gaps which we enjoy, though these gaps in our mental space and time are unfilled by mental events. In the external world two events of different date and place are observed as connected by a stretch of time or space however much foreshortened. These conditions are not presented in enjoyment. We must leave the problem for the present at this point, to resume it later.[17] It is enough to have shown what it really is, and that it offers no support to animism but rather, however difficult of solution, it in fact admits no solution at all unless mind is identical with some physical counterpart and is connected by some physical connections which need not necessarily be themselves mental ones, carrying the mental quality.
Divided consciousness and the unconscious.
The second of these problems, that of divided consciousness and of the unconscious, presents great difficulties to the psychologist and requires expert knowledge of special cases for adequate discussion. All that I can hope to do here, or need to do, is to indicate on
(26) what lines a solution might be sought in accordance with the view of identity between the conscious process and its neural correlate ; with the additional principle that such neural counterparts of mental processes are parts of a larger neural structure. The question of divided personality is more manageable than that of the unconscious. Whether the personalities alternate or coexist, it would seem that the normal personality, that is the total consciousness, is dissociated ' ; and it is not difficult to suppose that normal lines of connection between processes which are normally continuous, are for some reason barred or broken. In this way groups of mental processes with their neural basis are formed which have no complete connection with one another ; though they may and do in certain cases overlap, each for instance using the common speech apparatus. They are comparable to those systematised groups of mental processes which constitute interests, when in persons of normal condition these interests are exercised almost in independence of each other, the week-day mind and the Sunday mind which in many persons seem to have so little to do with each other. Suppose the separation of these interests to become absolute ; each interest would then constitute a separate personality of a limited kind. So in the body politic there are groups which almost ignore each other, and have different standards of feeling and conduct. Such separate personalities are called by a happy term co-conscious,' for in their case there is no good evidence to doubt that the split-off group really possesses a consciousness of its own, and the one person may treat the other very much as one normal person treats another with whom he has no such bodily alliance. That these co-conscious personalities mean the blocking of normal physical paths of communication (generally no doubt at the conscious level, as where there is actual loss of memory for tracts of a life), but possibly also at lower levels, is indicated by the process of restoration, where that occurs, of the original unity. Such restoration may assume a much more consciously deliberate shape than it probably possesses. Thus in the famous case of Miss
(27) Beauchamp' and her demon Sally,[18] the ingenious physician persuades the demon to abdicate in favour of the rightful possessor of the body. This act of resignation on the part of the demon, who is by no means a good demon, but selfish and somewhat malignant, probably is only a pictorial representation of the fact that the blocked lines of association belonging to the original personality are becoming permeable once more.[19]
Now where the original unity breaks up into two persons, A and B, and where A, as sometimes occurs, does not happen to be aware of B as a foreign person, A is unconscious of B, but inquiry shows that B is itself a consciousness. A's unconscious turns out to possess a consciousness of its own. But it by no means follows that we may extend this precedent and assume, where-ever what is unconscious can under certain conditions emerge into consciousness, that therefore the unconscious condition was all the while mental. We are here dealing not necessarily with pathological minds, but with the commonest facts of the normal mind. Thus incidents completely forgotten may at some time swim into memory, but must we assume that these processes were all the while preserved, not indeed as conscious but as an unconscious department of the mental ? Dreams, as is now well known, may be an expression of tendencies in the dreamer's mind which cannot be expressed overtly, but which subsequent analysis of the person's mind shows to have been there somehow preserved and seeking expression in the person. Evidence of this sort has become so abundant and has been marshalled with so much skill by Dr. Freud that to many it would seem natural to disregard the scientific scruples of those who in the face of such facts still question whether a truly
(28) unconscious state is ever mental, is ever, that is to say, more than a neural condition which may under appropriate circumstances lead to a conscious condition, and because this is so, may justly be called psycho-physical without being psychical. The other view leads to the conception of a larger mind of which the conscious mental states are but the appearance, somewhat in the fashion of a thing-in-itself, embodied no doubt in the neural structure, out of whose mysterious depths mental conditions emerge into the light of day. One may be very sensible of the enormous value for pure psychology (for I am not concerned with the therapeutic side of the matter) of Mr. Freud's discoveries without necessarily pledging oneself to belief in the existence of an unconscious mind.[20]
On the contrary, with the identity interpretation of the relation of mind and neurosis, a mental process may leave its traces in a neural form which is purely physiological. A memory may remain latent as a physiological trace or disposition, awaiting the touch of an appropriate stimulation to take on the full vividness and complexity of a conscious memory. At what level an experience is preserved it may not be easy to say. Possibly at the highest level ; but possibly also a conscious process may be registered in a lower level of the vital structure which subserves the mind. On the view that mental processes are also vital and therefore connected with the rest of the vital nervous structure, this proposition presents no difficulty. Thus we may have neural dispositions at lower levels than the conscious level, which may at any time be completed neurally and so call into play the action of the higher level. They would thus form a permanent undercurrent of the mental life, but would remain purely physiological till called upon to enter into the psychical neural constellation. For this reason they may be termed psycho-physical to indicate their essential continuity with what is psychical, but there is some risk that the expression may be misunderstood to imply the presence of a psychical factor. I prefer to speak of
(29) physiological dispositions, which are in themselves not psychical but may emerge into consciousness. Thus it would seem better to distinguish what are strictly mental dispositions, that is conscious plans, from dispositions secondarily acquired, automatic habits, which may remain entirely below the level of consciousness. With this explanation we can understand how a mental, that is a neural process at a certain level, may either become so lacking in intensity or so much disconnected with other processes as no longer to carry with it consciousness or may be replaced by and registered in a subjacent part of the structure ; and at the same time how owing to their continuity with the mental level such purely physiological conditions affect the course of the mental life and on occasion enter into it. Just so, at an even extremer remove from the mental life, the state of the nutrition, though it may not be psychically perceptible, may affect the working of the mind. Instead then of the mythological or at least hypothetical larger mind of which the conscious mind is only a part or an appearance, we should have a very palpable and unhypothetical neural system (itself a part of the whole organism) of which the workings of a particular part correspond to and in fact are consciousness, and any part of which may affect consciousness or may register the traces of past experiences.
Hence, to take an instance or two from a field whose details are matter for the specialist, it does not follow that because analysis after the event discloses the presence of a feeling in a dreamer's mind which disguised itself in the " manifest content " of the dream, that that feeling was present in a mental form. The physiological tendency may have been enough, for example the stirring of some organic process contained within an emotional condition. In psycho-analysis the inhibition is removed which prevented the tendency from coming to the surface in its natural form. It may well happen that ideas, for instance of decorum, set going by the physiological stirring of a tendency reputed immodest, may give a different turn to the tendency. From this point of view the machinery of the " censorship " exercised over the
(30)unconscious wish may be only a mythological or pictorial way of representing something very real which is going on in some part of the neural structure, but does not imply that all of it is mental. In the same way in negative hallucinations where a patient is told not to see cards with odd numbers of. pips, though it is evident he must distinguish odd cards from even ones in order to notice only the even ones, it does not follow that he sees the card with odd pips and then suppresses the perception ; the visual stimulus may be suppressed or inhibited by his instructions before it reaches the mental level of development.
It is by no means asserted that, where there is unconsciousness ' which
can be seen to be conscious under certain conditions, it is really
purely physiological. On the contrary, it may be co-conscious. I am only
pleading that we must choose between the conscious (which includes
subconsciousness in the sense that word sometimes and perhaps most
conveniently bears of what is in consciousness but indistinctly
separable from the mass of mental experience) and what is not mental at
all but purely physiological though it remains continuous with the
mental and may affect the mental. The truly unconscious is not mental at
all, though continuous with it ; if it is mental it is co-conscious. It
is only for the expert to say when there is co-consciousness and when
there is not. Accordingly, on the statement here adopted I find myself
in agreement with a passage of Dr. Morton Prince,[21]
which I will conclude this subject by quoting : " We can say at once
that considering the complexity and multiformity of psycho-physiological
phenomena, there would seem to be no a priori reason why all
subconscious phenomena must be the same in respect of being either
co-conscious or unconscious ; some may be the one and some the other. It
is plainly a matter of interpretation of the facts and there still
exists some difference of opinion." By unconscious processes the writer
means processes which are wholly unconscious, that is, are purely
physiological.
(31)
B. THE APPREHENSION OF OTHER MINDS
Acquired not by analogy, but by direct experience
Another topic which I discuss here, out of its proper place, but for convenience in exposition, is how we come to recognise each other as conscious subjects. In a previous chapter I was at pains to show that our belief in -the intimate connection of mind with brain was founded on direct experience ; though that experience was helped out by reflection, as all our experience is ; the issue of such reflection upon experienced data, some of them enjoyed, some contemplated, has been to identify the mental process with a certain constellation of physiological processes. I shall now try to indicate what the experience is on the strength of which we believe in other minds than our own. For without some direct experience of other minds such recognition does not occur. The existence of other minds is commonly regarded as an inference by analogy from the outward behaviour of other persons' bodies. Their gestures, actions, and speech in various circumstances resemble our own in those circumstances, and we regard them, it is said, as proceeding from a consciousness like our own. Now it is true that when we already have the notion of other minds, we interpret outward behaviour on the analogy of our own experience, and can thus sympathetically enter into their minds in all manners of refined and subtle interpretation. But in the first place the doctrine in question cannot apply from the nature of the case to unreflective animals, such as dogs, who certainly appear in some of their behaviour to recognise other dogs as of the same kind as themselves.
And in the next place it is flatly at variance with the history of our minds. It implies that we begin with a knowledge of ourselves and construe foreign selves in that likeness. Now it is almost a commonplace that the reverse is rather the case, that our reflective consciousness of ourselves arises in and through our consciousness of
(32) others. We are led, not of course to the enjoyment of ourselves but to noticing ourselves, through intercourse with others : the knowledge of ourselves and that of others grow up together. Our own individuality stands out for us against a background of other persons. Were we alone in a non -conscious world, we should enjoy ourselves and feel success and disappointment, but we should hardly experience ourselves as individual persons. But what is more important, mere inference by analogy cannot account for our original recognition of other minds. For the idea of a foreign consciousness, unless directly supplied by some experience to that effect, is something to which we have no clue in ourselves. We enjoy our own consciousness and our own consciousness only, and we do not contemplate it, but only our bodies. The idea of a consciousness not our own belonging to the body of some one else would be a sheer invention on our part. How should we invent such a conception of something totally new, if foreign consciousness were not in some manner revealed to us as such ?[22] For it is safe to assert that we never invent in that sense, but only discover, though we may combine the materials we already know in all sorts of new combinations. We have then to search for the experience which assures us not inferentially but directly of other minds.
The experience is of sociality
That experience is a very simple and familiar one, the experience of sociality, and has a double aspect. Our fellow human beings excite in us the social or gregarious instinct, and to feel socially towards another being is to be assured that it is something like ourselves. We do not first apprehend that another being is a mind and then respond to him, whether positively as in affection or negatively as in aversion ; but in our tenderness or dislike we are aware of him as like ourselves. Just as the emotion of fear or the instinct to run away from
(33) certain things discovers them to be dangerous, the cognitive apprehension being given to us only in so far as we practise a certain response, so in seeking the company, or avoiding it, of our fellows we are aware of them as like ourselves. But while without the social instinct we should not be led to this apprehension, we do not experience the satisfaction of the instinct of sociality till we have the experience that the creature towards which we act socially reciprocates our action, either by co-operation or rivalry. The emotion of sociality is a double-sided one ; it is a response on our part to the other being, confirmed by a response on his part to us. The double experience is necessary to sociality ; it takes two persons to make friends or two persons to make a quarrel. Without the instinctive response we should seek nothing from the other ; without the co-operation we should not be aware of him in the fullest sense as our fellow.[23]
Instances upon this merely instinctive level are the experiences of parental or filial affection, or sexual love, competition in pursuit of prey, or jealousy. We do not merely feel ourselves performing certain actions towards another but we want him, and in turn we find him playing his part in the joint experience in which we are both concerned. Without this reciprocation, our instinctive action would not have its peculiar flavour. Our social feeling towards him is the divination that he is like ourselves ; his reciprocation confirms it and makes
(34) it assurance. Thus we feel tenderly to a child as we should not feel towards a soft warm cushion (the illustration is from W. James). But we do not feel socially towards him, the tenderness has not its distinctive flavour, except for the reciprocation of the child. It is felt more plainly towards an affectionate than towards a cold child, and felt more and differently towards a child than towards a puppy. It may be questioned whether we should feel tenderness to a fly in distress if we had not already acquired tenderness in respect of living creatures which can reciprocate. There is, to take a different example, all the difference between grasping a hand which returns the pressure and grasping an unresponsive piece of flesh in the shape of a hand. It seems to us inhuman and disappoints our expectation of a return, and we wonder whether we are not shaking hands with a fish or a statue. To have the warm human experience we require reciprocation. Again, rivalry for the possession of food is a different experience from appetite for the food ; it contains the experience of jealousy or hate. Or again, if the rival is inanimate and cannot participate with us ; when for instance a cigar which I am smoking goes out I may be disappointed, but if it is knocked out of my mouth by a person I am angry. When the dog's bone rolls away from him he grasps it more firmly ; but if another dog or a man seizes it, he growls. The experience of another man's trying to get the same thing as yourself is a different experience from mere obstruction or difficulty in obtaining the object, and is the suggestion that he too wants it. It is of course true that when the experience of real rivalry has become familiar the obstructing inanimate agent may also be credited with consciousness ; and the dog may be angry if his bone slips or the man if his cigar goes out, or he may, like Sir Walter Scott, say that a letter which he cannot find has been hidden by the Devil. But he must have experienced rivalry to begin with. Once more, the feeling of love to the opposite sex is not the same when the love is not reciprocated, and accordingly love is different from mere selfish lust though even the mere animal satisfaction
(35) implies too complementary action of the other party.[24] A lover may of course feel genuine love when it is not returned, but his expectation or hope is for reciprocation, and his disappointment implies that the person is capable of returning the emotion though he is not the chosen object.
Thus it is because we are social beings and have the social instinct that we become aware of others as like ourselves and the possessors of minds. The animals, like ourselves, are aware of each other as like. But their consciousness of the likeness being without reflection amounts to nothing more than behaving towards each other as if they were what we call alike. Since it is sociality which gives us this assurance, the consciousness of other minds comes to us from our relations to one another and we do not learn so directly from animals that they have minds. Now in this experience that other humans excite our social desires and in turn satisfy them, which gives us the assurance that they also are minds like ourselves, it is not their similarity of behaviour to us which describes the situation into which I and another human enter. Hence the radical mistake of supposing that analogy of behaviour assures us of the existence of other minds. In general the part which the two participants in the social situation play is not the same but different ; the child's response to the mother is not the same as the mother's caresses. In some cases, as in struggle for food or fighting for a female, the acts may be in most respects alike.[25] But the likeness of behaviour is not a necessary
(36) incident. What is necessary is that the whole situation, of going out on the part of one person, does not exist without participation of both, and consequently the experience of either is incomplete without the response, whether it is by way of help or hindrance, of the other. We become aware in this direct experience of something like ourselves.
The grades of such experience
The primary concerns of life and its appetites, and the simplest occupations of primitive man or the animals supply material for this experience of other minds. Such recognition is in the main instinctive, that is, is upon the instinctive level of life. On the basis of this experience the savage or the child or the animal even, may impute personality or something like it to inanimate things, the doll or stocks and stones or the wind and the sun. This is an act of projection which is perfectly intelligible when the mysterious object, a foreign mind, has been discovered by revelation of it through such experiences as have been described. It is the extension of the notion of a foreign mind to things which behave in some ways like persons or ourselves. But, intelligible as an extension of something already discovered, it is not intelligible as a foundation for the original belief in a foreign mind.
Psychologists have explained for us in detail how our consciousness of others changes, not only in extent but in grade, with our years ; how for instance the father is to the child at first hardly more than a vague and unfathomable and arbitrary being, but as the child measures itself against its equals it comes in the end to understand him and to conceive him more precisely as a person like himself. All this too is intelligible as a further incident in the growth of the original fundamental awareness of a mind not our own.
In the reflective growth of the apprehension of the minds of others we are soon beyond those simple situations on the instinctive level with which we have
(37) hitherto been dealing. We make ourselves intelligible to one another by speech so that external objects described by one party are brought before the mind of the other. Mutual understanding by speech in reference to objects common to us is the most pervasive experience of reciprocity ; and to this is added the direct description of our own mind to another person. On the speculative side we have co-operation of many minds in the pursuit of knowledge or science. On the practical side we have the combination of wills in conduct, with its judgments of the kinds of action which make common intercourse tolerable and good. Moral judgments and scientific agreement are the highest expressions of the existence of other minds which we experience directly and on this level 'acknowledge.'
But although we thus have direct experience of the existence of minds in others, such experience is not knowledge derived either from contemplation of the external or enjoyment of ourselves. We can enjoy only our own mind and not the mind of another. On the other hand we do not contemplate our own mind as if it were an external object, much less the mind of another. Thus I am not aware of B's mind as I am aware of his body, so that I should be able to inspect it and say what it is. Yet experience assures me that he has a mind. What sort of a mind it is, how the other mind feels in a given situation, I am left to divine sympathetically on the basis largely of analogy with my own. But that a mind is there, is assurance. It is not invented by inference or analogy, but is an act of faith forced on us by a peculiar sort of experience. It is only the details of its nature into which we have to enter symbolically by imagining ourselves in the situation of the other person. It is sufficient for our purposes to have indicated that their existence is revealed to us by experience directly and by what experience it is so revealed.
