Part I: The Mental Life
Men evolved from apes, and apes from more primitive animals, and the primitive animals evolved from the soup of inanimate atoms which consolidated to form the Earth some four thousand million years ago. Although there is much uncertainty about the exact stages and mechanisms involved, the fact of evolution is evident. Even more evident, to my mind, is the fact that what has evolved is different, radically and qualitatively, from that from which it has evolved. Rocks and rivers are not conscious; they do not have thoughts, sensations, and purposes; but men, and some animals, do have thoughts, sensations, and purposes. And having a thought or a sensation or a purpose is not just having some physico-chemical event occur inside one of greater complexity than the physico-chemical events which occur in rocks and rivers. It is not the same sort of thing at all. The mental life of thought, sensation, and purpose may be caused by physico-chemical events in the brain, but it is something quite different from those events: it is rich in inbuilt colour, smell, and meaning. The process of evolution so rearranged the atoms and molecules as to bring about creatures with a life of conscious experience, which is something altogether new in the history of the universe.
Once the thinker takes seriously this vast evident qualitative difference between inanimate things on the one hand, and animals and men on the other, two things will strike him about conscious experience. The first is the fairly evident fact that there is a continuity in experience. The person who has these experiences today has different experiences tomorrow, including ones in which he remembers the experiences of yesterday. This continuity of experience may indeed be caused by continuity of brain matter, but it is not the same thing as it. The second thing is the fairly evident fact that conscious experience is causally efficacious. Our thoughts and feelings are not just phenomena caused by goings-on in the brain; they cause other thoughts and feelings and they make a difference to the agent's behaviour. Apparently, people have trains of thoughts, and present thoughts are suggested by previous thoughts; and an agent acts in the world as he does because of his purposes which he seeks to fulfil.
These two further differences between inanimate things on one hand and animals and men on the other are not quite as evident as the fact of consciousness itself, and more argument is required to substantiate their existence: that will be provided in this book. The theme of the book is the nature and source of the differences between the inanimate objects which alone existed on the Earth at its formation, and the animals and men which have subsequently evolved. Part I will analyse the different facets of the mental life, enjoyed by animals as well as men—sensations, thoughts, purposes, desires, and beliefs. I shall argue, contrary to recent philosophical objectors, that evident appearance is not delusory—there really are mental events and states different from brain processes and observable public behaviour; and they really do make a difference to the organism's public behaviour. Part II will argue that we can only make sense of the continuity of this conscious life by supposing that there are two parts to a man (and to many another animal)—a body and a soul (or mind). The body is an ordinary material object, and so is that crucial part of it—the brain; but the latter is connected to a soul which is the essential part of a man, and which is the part which enjoys the mental life (i.e. which is the subject of sensation and thought and the originator of actions). The evolution of consciousness is the evolution of organisms with souls which are conscious and which interact with the body. The occurrence (though not the details) of the mental life of the soul is however dependent on physical processes in the brain—at any rate at present.
Part III will go on to consider the differences between the mental life of men and that of other animals. I shall describe two evident differences—that men have powers of complex and logically ordered thought and an awareness of moral goodness and obligation, lacking to animals. And I shall argue for the existence of two further differences, not immediately evident—that men have free will in the sense that their choices are not totally predetermined by their brain-states or anything else; and that a human soul has a structure or character which is formed in part through the brain to which it is connected, but which acquires some independence of that brain. No doubt the different facets of animal mental life appeared at different stages of evolutionary history—first perhaps there evolved animals who have sensations, then animals who have also purposes, desires, and beliefs, then animals who have, as well, conscious occurrent thoughts. And if evolution can produce animals with characteristics qualitatively different from those of inanimate things, it would not be surprising if it went on to produce men with substantial further qualitatively different characteristics from the higher animals. I shall argue that it has done so.
The physiologist studies the development of the first cell of each new human baby into a full-grown adult. The evolutionary biologist studies the forces which have formed the genetic structure of such a first cell. But relatively seldom do either of these scientists point out that their descriptions and explanations cover only the evolution of the physical characteristics of man, and that they give no account of the evolution of the most important characteristics of man—the characteristics of his conscious life, his feelings and desires, hopes and beliefs, those characteristics in virtue of his possession of which we treat men, and think that we ought to treat men, as totally different from machines. Most philosophers of the past four centuries have been well aware of the difference between the conscious life of a man and goings-on in his body, but their views have relatively seldom made any significant difference to the writing and teaching of biologists and physiologists.
Scientists have tended to regard the life of conscious experience as peripheral, not central to understanding man. But there is so much and so rich human experience, and experience which is apparently continuous and is causally efficacious, that this attitude will not do. His life of experience has to be taken seriously if we are to understand man. Scientific revolutions occur when data and coincidences previously regarded as unimportant are taken seriously and made the focal point of understanding. This book takes seriously the fact of human conscious experience, its continuity and its causal efficacy—and around these facts, hitherto regarded as peripheral, builds its understanding of man and his evolution. While I shall attempt to describe the differences between men and machines, I shall not be able fully to explain their origin; and indeed I shall produce an argument to show that it is most unlikely that anyone will ever be able fully to explain their origin in terms of a normal scientific explanation. The prospects for a fully explanatory super-science which embraces the mental world as well as the physical world are poor. But we must not fall into the trap of believing that that which we cannot explain (at any rate by a normal scientific pattern of explanation) does not exist. The conscious life evidently exists—that we have sensations and thoughts, feelings and hopes is the most evident thing that there is.
Each of the many issues which I discuss in this book is normally the subject of a book to itself. A philosopher will write a book on sensation, or on belief, or on moral awareness. I am conscious of my temerity in writing one book concerned with all the differences between man and the inanimate and the story of their evolution; and I am well aware of the inadequacy of the treatment which I give to many detailed issues. But I am also aware of the need for an overview of the whole field, and of the difficulty of making plausible a view on some of the issues which I discuss towards the end of the book (e.g. the freedom of the will) without also stating and justifying a view on the issues discussed earlier. Such is my excuse for treating so large a subject within the cover of one volume.
Some Technical Terms
So far I have described my subject matter in vague and ill-defined terms. It is time to introduce more precise technical terms.
My inquiry is into the nature and evolution of man. A man is a member of the human species (and my use of the short and convenient English word ‘man’ which is also often used to denote a male member of that species carries no implications about any superior status possessed by the males of the species). I also use the word ‘person’. As I shall use this word, a person is anyone who has all the facets of consciousness which men possess, whether a member of the human species or not. Thus, creatures from another planet with a conscious life like ours would be persons, but not humans; so, too, would angels. If I am right in my view that there are significant differences between human consciousness and the consciousness possessed by other animals (e.g. that the latter can only have thoughts of very down-to-earth kinds), it will, however, follow that such animals are not persons. As I shall use the words, I shall make it a matter of definition that a ‘man’ has a human body, but, I shall argue in Chapter 8, it is not part of our current understanding of ‘person’ that a person has to have a body, let alone a human body; and I shall not impose that restriction on the notion of ‘person’. I thus leave it open to argument whether the persons who are men can lose their bodies or acquire non-human bodies, and so cease to be men while continuing to be. I sometimes use the more general terms ‘subject’ (to refer to any one who has a mental life) and ‘agent’ (to refer to any one who performs intentional actions), which apply to persons and most animals. In future I shall use the word ‘animal’ in the narrower sense in which men are distinguished from animals, although, of course, in a wider sense man is a species of animal.
I follow normal philosophical usage in understanding by a ‘substance’ a component of the world which interacts causally with other components of the world and which has a history through time. Tables and chairs, stars and galaxies, cabbages and persons are substances. Substances have (monadic) properties—such as being square or yellow, or having a mass of 2 lbs. They also have polyadic properties, or relations to other substances, such as being taller than, or lying between. ‘Taller than’ is a relation which relates two substances; ‘lying between’ is a relation which relates three substances. (One object lies between a second object and a third object.) I shall understand by an ‘event’ the instantiation of a property (either a monadic property or a relation) in a particular substance or particular substances at particular times—such as this tie being now green, or having a rough surface; or John being taller than James last year; or Keele now lying between Birmingham and Manchester. Events are states of substances.
In philosophical terminology, I understand by ‘events’ token events, particular occurrences; as opposed to properties which are universals, in the sense that the same property can be instantiated in many different substances on many different occasions. My use of the word ‘event’ is not that of ordinary usage. Ordinarily we think of events as changes in the properties or relations of substances—such as an object changing from being red to being green, or changing from being on my left to being on my right. But a list of events in my sense—of the properties and relations possessed by substances at particular times—would allow one to deduce which events in the more normal sense had occurred to those substances. If you know that my tie was red at 10.00 a.m. and was green at 10.01 a.m., you can deduce that an event in the normal sense of its changing its colour occurred during the period 10.00–10.01.
Properties, and, more obviously, events may themselves have properties, including relations to other properties and events. One event may be related to another event by the relation of ‘occurring before’ it, and by the relation of ‘causing’ it.
It is a complicated task to give a precise definition of a material object, but for our purposes a rough characterization will suffice.1
Rocks, tables, chairs, plants, houses, and similar inanimate things are material objects. So is anything which is part of a material object (e.g. an atom), or anything of which such material objects are themselves parts (e.g. a planet). A material object excludes all other material objects (apart from objects which are part of it, or of which it is part) from the space which it occupies. The human body, consisting of atoms, is thus a material object. And so too is man (indeed, he is the same material object as his body)—unless he has a part which is not a material object. All material objects are substances, but a crucial issue is whether there are substances other than material objects, things which interact with material objects, but which are not themselves material objects and perhaps do not even have spatial position.
Properties and events may be physical or mental. I understand by a ‘physical property’ one such that no one subject is necessarily better placed to know that it is instantiated than is any other subject. Physical properties are public; there is no privileged access to them. Thus having a mass of ten pounds, being eight feet tall, and being square are all physical properties. So too are the typical properties of neurones in the brain—being in such-and-such an electrical state or releasing a transmitter substance. Anyone who chooses can find out as surely as can anyone else whether something is eight feet tall, or in a certain electrical state. Physical events are those which involve the instantiation of physical properties. ‘Mental properties’, as I shall understand the term, are ones to which one subject has privileged access, which he is necessarily in a better position to know about than anyone else. Some philosophers, as we shall see, deny that there are any mental properties in this sense. But it does rather look at first sight as if properties, such as being in pain or having a red after-image, are mental, for any person in whom they are instantiated does seem necessarily to be better placed to know about them than does anyone else. For whatever ways you have of finding out whether I have a red after-image (e.g. by inspecting my brain-state or studying my behaviour) I can share; and I have an additional way of finding this out—by my own awareness of my own experience (an awareness which may or may not be fallible). So it looks as if there are mental properties, distinct from physical properties. ‘Mental events’ are events which involve the instantiation of mental properties (e.g. John being in pain at midday yesterday).
There are properties, and so events, which look to be mental on this definition, which can be analysed in terms of a physical component and a mental component. These properties and events we may call ‘mixed’ mental properties and events. Thus ‘saying “hallo”’ is a mixed property, for my saying ‘hallo’ consists in my intentionally seeking to bring about the sound ‘hallo’ (a mental event) causing the occurrence of the sound ‘hallo’ (a physical event). It is the property of the instantiation of a certain mental property causing the instantiation of a certain physical property, which is possessed by the substances which are persons who say ‘hallo’. (Or at least so it is, if there are, as there appear to be, mental properties; and if, as appears, their instantiation causes the instantiation of physical properties. These issues will be explored more fully in due course.) Those mental properties which cannot be analysed in part in terms of a physical component I term ‘pure’ mental properties. ‘Being in pain’ and ‘desiring to eat’ seem to be such pure mental properties. In talking henceforward of mental properties I shall understand thereby (unless I specify otherwise) pure mental properties; and I shall understand by mental events the instantiations of pure mental properties.
Three Views on the Mind/Body Problem
The technical terms which I have now introduced allow me to expound the crucial issue of the first two parts of the book in more rigorous terms. Their concern is with the mind/body problem, the problem of the relation between a man's conscious life of thought and sensation, and the physical events in and around his body. On this issue there are three main positions which have been taken in the history of thought.
The first position, which I shall call hard materialism, claims that the only substances are material objects, and persons (including men) are such substances. A person is the same thing as what is loosely called his body (and his brain is the same thing as his mind). The only events which occur, the only things that happen in the world, are physical events, viz. ones which consist in the instantiation of physical properties in material objects. There are no mental events in the sense in which I have analysed this notion; for there are no events distinct from physical events to which the subject has privileged access. My being in pain or having an after-image may seem to be mental events, but really they are not-according to the hard materialist. Hard materialists differ among themselves as to which physical events those apparently mental events are. One school holds that they are brain-events—my having a pain just is certain nerve fibres firing in a certain pattern; my having a certain belief just is the existence of a certain nerve circuit in the brain. In recent times this doctrine has been known as Mind-Brain Identity Theory. The other school of hard materialists holds that talk about apparent mental events is talk about the subject's actual or hypothetical public behaviour, what he does and what he would do in different circumstances. For me to have toothache is for me to hold my jaw, be bad-tempered, arrange a dental appointment, etc. all when my tooth is somewhat decayed; and if asked, to say that I have toothache; and if I bite something hard, to cry out. My having the mental event just is the occurrence of the public behaviour which, ordinarily, we would say, it causes. This doctrine is of course known as behaviourism.
In chapters 2 and 3 I shall be discussing the nature of sensations—pains, visual sensations, auditory sensations, and so on. I shall be arguing that they, at any rate, are mental events in my sense; and in subsequent chapters I shall claim that there are mental events of other kinds. My sensations are no doubt caused by brain-events, but they are not themselves brain-events. My having a red after-image or a pain or a smell of roast beef are real events. If science describes only firings of neurones in the brain, it has not told us everything that is going on. For it is a further fact about the world that there are pains and after-images, and science must state this fact and attempt to explain it. Likewise sensations are to be distinguished from the behaviour to which they typically give rise. For people have sensations to which they give no expression—pains which they conceal or dream-sensations which they report to no one—and, if the sensations give rise to behaviour, the subject is aware of the sensation as a separate event from the behaviour to which it gives rise. The life of conscious experience seems a reality ignored by hard materialism.
The second position on these issues I shall call soft materialism. (It is sometimes called attribute or property dualism.) Soft materialism agrees with hard materialism that the only substances are material objects, but it claims that some of these have mental properties which are distinct from physical properties. Persons are material objects; again, a person is the same thing as his body, and his brain is the same thing as his mind. But persons (and their brains) have, as well as physical properties, also mental properties, such as feeling tired and having a visual sensation of such and such a colour and shape, whereas most substances such as tables and chairs have only physical properties. Mental events—e.g. my having a pain now—are different from brain-events; they are not physical events. Brain-events cause mental events. (Neurones firing in certain patterns cause me to have a red after-image.) And also perhaps mental events cause brain-events. (My decision to move my arm causes the brain-events which cause my arm to move.)
Soft materialism has appealed to the many philosophers and psychologists who hold that the unity of the self is constituted by the unity of the body without denying the evident fact that men are conscious. The basic difficulty however with soft materialism, as with hard materialism, is that there seem to be more truths about the world than the doctrine says that there can be. Hard materialism says that you have told the whole story of the world when you have said which material objects exist and which physical properties they have. But, as we have seen, there is also the issue of which mental properties are instantiated. Soft materialism says that you have told the whole story of the world when you have said which material objects exist and which properties (mental and physical) they have. However, full information of this kind would still leave you ignorant of whether some person continued to live a conscious life or not. Knowledge of what happens to bodies and their parts will not show you for certain what happens to persons. I shall illustrate this in Chapter 8 with the example of brain transplants. As is well known, the human brain consists of two very similar hemispheres, each of which is capable of performing many of the functions of the other; and people can survive when they lose much of one of the hemispheres. Now suppose one brain hemisphere is taken out of my skull and transplanted into the empty skull of a body from which a brain has just been removed; and the transplant takes, and we have a living person with a life of conscious experiences. And suppose that the other hemisphere is transplanted into a different empty skull, and that transplant also takes; so that we now have two living persons, both with lives of conscious experiences. Which would be me? Clearly, both would behave like me and make my memory claims; for behaviour and speech depends, at any rate in part, on brain-states. But both persons would not be me. For if they were both identical with me they would be the same person as each other (if a is the same as b, and b is the same as c, then a is the same as c) and they are not. They now have different experiences and different lives. Maybe the person with my right brain hemisphere is me, and maybe the person with my left brain hemisphere is me, and maybe neither is me. We cannot be certain. The point, which I shall be developing at length, is that mere knowledge of what happens to bodies does not tell you what happens to persons. Hence there must be more to persons than bodies. I shall therefore be arguing that a man living on Earth is a substance which consists of two substances, his body and his soul. The body is a material body, but the soul is not a material object or anything like it. (It occupies no volume of space.) Body and soul are connected at present, in that events in the body affect events in the soul, and conversely. But the essential part of the man is his soul; a man consists of his soul together with whatever, if any, body is connected to it. Mental events which happen to the human being do so in virtue of happening to his soul; bodily events which happen to the human being do so in virtue of happening to his body. This is dualism, the position which I shall defend.
Dualism has, however, often been held, as by Plato and Descartes, in the extreme form of the doctrine that the soul has a natural immortality, i.e. that the soul has a nature such that it will continue to survive ‘under its own steam’ whatever happens to the body. I shall argue that, on the contrary, there can be no justified general account of the nature of the soul; all we can say is that under normal mundane conditions the functioning of the soul requires the functioning of the body. My form of dualism might be called ‘soft dualism’.
Principles of Inductive Inference
For our knowledge of the mental life of others, of mental states which exist when no one is conscious of them, and of what causes what we are often dependent on inductive inference. That is, we observe or experience certain events and these are evidence for the occurrence of other events which we do not observe or experience. They are evidence for the latter in that they make their occurrence more probable or likely than they would otherwise be (i.e. they confirm their occurrence), and sometimes they make them very probable indeed; and so the enquirer ought to believe. When are some events evidence for other events?
The first and most general principle of inductive inference is the Principle of Credulity
: that in the absence of counter-evidence probably things are as they seem to be, ‘seem to be’, that is, in the epistemic sense. There is an important class of verbs for describing an agent's awareness of the world—the general verbs ‘appears’ and ‘seems’; and verbs for special senses, ‘looks’, ‘sounds’, ‘feels’, ‘smells’, and ‘tastes’. There are two crucially different senses of each of these verbs, distinguished by Chisholm, the comparative and the epistemic sense.2
An object looks φ in the comparative sense to a subject s
if it looks to s
the way φ things normally look (i.e. its visual appearance is that normal for φ things); an object looks φ in the epistemic sense to s
if (because of the way it looks in the comparative sense) s
is inclined to believe that it is φ. By saying that s
to believe that the object is φ, I mean that he will believe this in the absence of further evidence—e.g. what someone else tells him. The penny lying on the table viewed from an angle looks elliptical in the comparative sense (because it looks the way elliptical things normally look, viz. look when viewed from above), but it looks round in the epistemic sense to most of us—because (on the basis of the way it looks in the comparative sense) we are inclined to believe that it is round. Similarly for the other verbs. An object seems φ to s
in the epistemic sense if (on the basis of the way it seems in the comparative way) s
is inclined to believe that it is φ.
The principle of credulity states that if (in the epistemic sense) it seems to you that you are seeing an orange, or opening a tin of peas, or whatever, then probably you are seeing an orange or opening a tin of peas, or whatever, unless you have good reason for supposing that you are subject to illusion: and so you ought to believe. Such good reason will be the conflict of what seems to you to be the case with other things which seem to you to be the case—e.g. it can't be an orange if you can put your hand through it; and if it seems to you that you have put your hand through it, that is reason for supposing that you are subject to illusion in supposing that you are seeing an orange.
Without this principle, there can be no knowledge at all. If you cannot suppose that things are as they seem to be unless some further evidence is brought forward—e.g. that in the past in certain respects things were as they seemed to be, the question will arise as to why you should suppose the latter evidence to be reliable. If ‘it seems to be’ is good enough reason in the latter case, it ought to be good enough reason to start with. And if ‘it seems to be’ is not good enough reason in the latter case, we are embarked on an infinite regress, and no claim to believe anything with justification will be correct. If the fact that something looks square is not good reason for supposing that it is square without it being shown that in the past things that looked square have usually proved to feel square, behave in a square-like way, etc., the question arises as to why we should believe that things were thus in the past, and the answer must be that it ‘seems’ to us that we so remember. And if seeming is a good reason for believing in the latter case, then looking is a good reason for believing to start with. It is a slogan of science that we should rely on ‘the evidence of our senses’, on ‘experience’; the principle of credulity crystallizes this slogan more precisely.
We should not, however, believe that things are as they seem when there is counter-evidence—either that in a particular case we are subject to illusion, or that in a particular range of cases (e.g. where it seems to men that they see round corners, or backwards in time) human experience is unreliable. But this counter-evidence itself will arise from trusting experience, from discovering that where people report seeing round corners things are not (it seems epistemically) as they report. There is no avoiding ultimate reliance on the principle of credulity. The rational man is the credulous man—who trusts experience until it is found to mislead him—rather than the sceptic, who refuses to trust experience until it is found not to mislead him.
The principle of credulity that an individual ought to believe that things are as they seem to him is backed up by the Principle of Testimony: that individuals ought to believe the reports of others about how things seemed to them, and so (given the principle of credulity) that things were as they report—in the absence of counter-evidence. That is, other things being equal, the reports of others are probably true. Only if we assume that people normally tell the truth, will we ever understand what they are saying. The child learns to understand his parents, by finding some feature of his environment which is present when they utter some sentence (e.g. they say ‘it is raining’ when it is raining) and then, supposing that they are seeking to describe that feature truly, he comes to learn what that sentence means. But without using the principle of testimony he could not even understand what was said. Of course, ‘other things’ are not always ‘equal’. We find by experience that certain persons, or persons in certain circumstances, are not to be trusted. But what the principle states is that we must assume trustworthiness in the absence of counter-evidence.
The principles of credulity and testimony give the enquirer a vast data base. From it he constructs his theories about how the world works—what there is in it and how it operates. But our data base is only a finite collection of data, a finite number of events which we reasonably believe to have occurred. One can construct an infinite number of different theories compatible with that collection of data, theories about unobservable substances and properties which bring about the observable events, theories about the laws of nature which determine which events bring about which other events. Choice among such theories is determined by the Principle of Simplicity. Among such theories we take the simplest one as that most likely to be true—or, more precisely, in a given field, we take as most likely to be true the simplest theory which fits best with other theories of neighbouring fields to produce the simplest set of theories of the world. The simplest theory is that which postulates few substances, few kinds of substances, mathematically simple properties of substances determining their mode of interaction with other substances (i.e. mathematically simple laws of nature). Faced with a set of identical footprints, we could postulate that each was caused by a different man wearing a qualitatively identical shoe, or we could postulate that all the footprints were caused by one man. The latter hypothesis being simple is more likely to be true. Faced with certain points on a graph, being measurements of the value of one variable for a given value of a different variable (and given no other background information of how these variables are likely to interact), we draw the simplest (i.e. normally the smoothest) curve through the data-points, and regard it as more likely that future measurements will lie on that curve than that they will lie on some other curve. The simplest theory provides the ‘best’ explanation of the data, that is, the explanation most likely to be the true explanation of why the data are as they are.
Indeed, so convinced are we that the simplest theory is that most likely to be true, that we are prepared to regard some of our initial data as slightly inaccurate and a few of them as wildly erroneous in order to get a simple theory of a field. We seek not the simplest curve which passes through all our data-points, but the simplest curve which passes close to most of our data-points. The enquirer regards as best supported by evidence that simplest theory of the field which has the consequence that almost all of the claims of observers about how things seem (epistemically) to them turn out to be (more or less) correct. Science is prepared to correct a few observational reports in the light of the simplest theory compatible with the vast majority of observational reports.
The principle of simplicity thus shows what is to be regarded as ‘counter-evidence’ to the operation of the principle of credulity. We should not believe that things are as they seem to be in cases when such a belief is in conflict with the simplest theory compatible with a vast number of data obtained by supposing in a vast number of other cases that things are as they seem to be.
Any belief which we reach through application of the principle of credulity is corrigible. Suppose a certain metal object viewed from a certain angle looks (in the epistemic sense) elliptical. I therefore come to believe that it is elliptical. But when I view it from several other angles it looks (in the epistemic sense) round and when I feel it it feels round. So I come to believe that when I perceive it on the latter occasions it is round. It is simpler to suppose that it has always remained of the same shape rather than suddenly changing shape (which would make it unlike other metal objects, which, use of the principle of credulity leads us to suppose, do not change shape suddenly). So I come to believe that it has always been round, and retract my original judgement that on a certain occasion it was elliptical. But my retraction arising from my use of the principle of simplicity, depends crucially also on my use of the principle of credulity on other occasions, and on the results produced by many uses of it outweighing the result produced by a single use. There is, I repeat, no other access to justified beliefs about the world except by means of the principle of credulity.
In attempting to understand the mental life of other men, we apply a principle which is a consequence of the principle of simplicity—the Principle of Charity
. Other things being equal, we suppose that other men are like ourselves—in the mental (or apparently mental) life to which similar stimuli to their bodies give rise and in the mental (or apparently mental) life which is followed by similar bodily responses. I believe that the principle of charity follows from the principle of simplicity, since it is simpler to postulate that organisms in so many ways similar to ourselves have similar connections between mental and bodily states to the ones which exist in ourselves than to suppose different connections to exist in different men. My claim that the principle of charity does follow from the principle of simplicity may be disputed by those who claim that the justification for our belief in ‘other minds’—that other men are not just robots but have a life of sensation, thought, etc.—is quite other than the justification for our belief in inductive extrapolation. I shall not argue the point here, as the issue of ‘other minds’ is a complex one.3
I shall simply use the principle of charity and assume, as we all do, that the principle is correct (whether or not it is independent of the principle of simplicity). Without this principle we would have no justification for believing that other men are conscious beings like ourselves. But with this principle we can infer not merely that there are ‘other minds’ but that they are similar to our own in various ways.
Any theory constructed from data by the principle of simplicity may be false, and may be shown to be false by subsequent observation and experience, but the principle which science uses is that the simplest extrapolation from certain data is the one which (given those data alone) is most likely to be true; the one which, for the time being, we ought to believe.
The above principles of inductive inference will be used from time to time in subsequent argument. They are, I suggest, the basic principles used by science.
THE MENTAL LIFE
If there is a mental life to which a subject of experience has privileged access, it is a rich and varied one. A man's mental events will include perceptions and sensations (of all the different senses), imaginings, memories and hopes, thoughts and feelings, dreams, desires, and beliefs. I shall however be claiming, by considering typical examples, that all other mental events are qua mental (i.e. in respect of the pure mental events which compose them), composed of elements of five kinds—sensations, thoughts, purposings, desires, and beliefs.
By sensations I mean experiences (other than beliefs) of the kind normally brought about by the senses, or ones similar thereto in experiential content, such as my experiencing the patterns of colour in my visual field, sensations of taste or smell, mild aches and pains, sensations of hot or cold in parts of my body; together with their pale imitations in my recalling memory images or my imagining imagined images. By thoughts I mean those datable conscious occurrences of particular thoughts, which can be expressed in the form of a proposition. Often these are thoughts which occur to a man, flit through his mind, or strike him without him in any way actively conjuring them up. It may occur to me—that today is Tuesday, or that this is a receptive audience, or that the weather is cold. I may, instead, on occasion actively bring about thoughts, maybe rehearsing a train of thoughts, to drum them home to myself, or hoping that some thought which I produce will spark off some new thought which solves all my problems. But thoughts are in the main uncaused by the subject.
By a man's purposings I mean his endeavourings to bring about some events, meaning so to do. Every human intentional action, everything which a man does meaning to do it, consists of the man bringing about some effect, or trying but failing to do so. Yet when the man brings about some effect, his active contribution may be just the same as when, unexpectedly, he tries but fails to bring about the effect. When I move my hand, I bring about the motion of my hand. Normally this action involves no effort and is entirely within my control. But on some occasion, I may find myself unexpectedly paralysed. My active contribution is the same as when I move my hand successfully, yet, because I fail, we say that what I did was to ‘try’ to move my hand. Normally we speak of ‘trying’ only when effort or failure is involved. Yet we do need a word which covers both the trying which involves effort or failure, and an agent's own intentional contribution to an action, when the performance is easy and successful. For this intentional contribution, for an agent's setting himself to bring about some effect (even when effort or failure is not involved) I will use the word ‘purposing’.
A man's beliefs are his view of how the world is, his ‘picture’ or ‘map’ of how things are. A man's desires are his natural inclinations to do things, experience things or have things—what he feels naturally inclined to do or seek, and so what he will do or seek but for a belief that he ought to be doing something else or that the pursuit of some other goal would be more in his long-term interest.
Among these suggested five components of the mental life there are, I suggest further, some crucial distinctions. Desires and beliefs are continuing mental states; sensations, thoughts, and purposings are conscious episodes. I understand by a continuing mental state a state in which the subject may be for a long period of time, including while he is totally unconscious. I understand by a conscious episode a part of the subject's (total) state of consciousness at a particular time. The subject's state of consciousness is a state of which he must be to some extent aware while he is in it. A subject's state of consciousness is the state consisting of all his experiences and purposings at a given time.
A belief that Edinburgh lies to the north of London, and a desire for success in an examination or revenge on an enemy, last while their subject is asleep or thinking of other things. Sensations, thoughts, and purposings are by contrast conscious episodes. Thoughts and purposes would not exist unless the subject was to some extent aware of them. I could not have the thought that it is John who is knocking at the door, nor could I sign my name intentionally, unless to some degree I was aware that I was having the thought or was purposing to sign my name. There are, however, degrees of awareness, and subjects can be only half-aware (subconsciously aware) of their thoughts and purposes. They can, I shall suggest, be totally unaware of particular sensations but only to the extent to which other conscious episodes hold their attention. A sensation would not be a sensation, a pain would not be a pain, if, in the absence of any other conscious episodes, the subject was totally unaware of its occurrence; nor would pains or after-images be sensations unless the subject could become aware of them, through reflecting on what he was experiencing.
Beliefs, desires, sensations, and thoughts are all passive events; purposings are active events. The former are passive in that they consist of some event happening to the subject, while purposings are active in that they consist of the subject intentionally doing something. Those conscious episodes which are passive, viz. sensations and thoughts, are experiences. Beliefs, desires, sensations, and thoughts are also, on the whole, involuntary, in that what happens to the subject is not something which he himself brings about. Beliefs, I shall be arguing, are always totally involuntary—we do not choose our beliefs; they come to us. (We can to some extent choose the topics about which we will have beliefs by choosing which topics to investigate; what we cannot choose is which beliefs we will have as a result of pursuing the investigation.) Desires, too, are things we find ourselves having; but here we can through assiduous cultivation change the pattern of our desires over time. Most sensations and thoughts which happen to us are not the result of choice; sensations assail our senses, and thoughts flit through our minds without being chosen. But we can, if we choose, produce sensations and thoughts at will—in the case of sensations by exposing our senses to the right stimuli or conjuring up a faint image of a sensation.
Thoughts and purposings and, less obviously, beliefs and desires are, I shall be arguing, intrinsically propositional, whereas sensations are not propositional at all. By the former being propositional I mean that they consist in an attitude to a state of affairs under a certain description, i.e. as described by one proposition but not as described by a logically equivalent proposition. (Two propositions are logically equivalent if of logical necessity whenever one is true the other is true and conversely. ‘John is two years older than James’ is logically equivalent to ‘James is younger than John by the number of years which equals the positive square root of four’.) A thought, for example, is a thought that a certain proposition is true or may be true or ought to be true. A purposing is a purposing that a certain proposition be made true.
Even if p
is logically equivalent to q
, the thought that p
is a different thought from the thought that q
and the one may occur without the other occurring. A thought or purposing is the thought or purposing it is in virtue of the proposition which it contains. Many writers have used the words ‘intentional’ or ‘intensional’ to do the job for which I am using the word ‘propositional’ but these words have a variety of meanings; and I hope that less confusion will result from my usage. By saying that thoughts or whatever are intrinsically propositional, I mean that this propositional character does not belong to the thought in virtue of some context in which it occurs (as it might be said that the propositional character of some spoken sentence of English belongs to it in virtue of the linguistic conventions of our society which give it its meaning), but is intrinsic to the thought, whatever the context of its occurrence.4