A Case for Dualism and Interaction

Howard D. Roelofs

Philosophy and Phenomenological Research, Vol. 15, No. 4 (Jun., 1955), 451-476.

Quoted from: http://links.jstor.org/sici?sici=0031-8205%28195506%2915%3A4%3C451%3AACFDAI%3E2.0.CO%3B2-Q

Philosophy and Phenomenological Research is currently published by International Phenomenological Society.


I have called this essay "a case" for Dualism and Interaction, rather than "the case" because in two senses that is all it is. First, the evidence here given is not all that might be offered. Second, and this is the more important, I do not regard my presentation as conclusive. So far as I have been able to discover, a conclusive demonstration of dualism and interaction as the solution of the mind-body problem is not to be had; and in the final section of this essay I shall offer a criticism of the position which, on the basis of our present knowledge, I nonetheless accept and maintain. How all this comes about will, I trust, be made clear and convincing by the essay itself.


Dualism and Interaction name a theory, a theory with rivals. In modern philosophy these rivals are conventionally two, Naturalism and Idealism. There is also the position which holds that the mind-body problem is not a genuine but only a pseudo-problem, and this might be called another rival theory in addition to those I have named. In any case, however, I do not propose to state and then criticize these rivals, whether they be two, three, or more, but I count upon the knowledge commonly available of all these theories to provide a setting for my exposition and substantiation of Dualism and Interaction. The common subject for which these theories offer their diverse interpretations is the unsolved puzzle of ourselves, the essential nature of man. What in man evokes and sustains these rivals is that man displays a prima facie duality in a unity. Each of us is a body; each of us is a mind; and each of us in being body and mind is not two but one. This dualism in a unity is the primary datum which all of us, regardless of which theory about man we profess, recognize and accept. Since my own position is labelled Dualism, it might be suspected that I am trying to win an initial advantage by this description. Dualism is what we start with, I may seem to be saying, and if anything else is asserted, the burden of proof is on those who diverge from Dualism. But I make no such claim. It is precisely because I do not wish to capitalize on this prima facie dualism, that I begin by calling attention to it. It is important that this initial dualism be recognized and accepted for what it is, no more, but also no less. I have sought diligently for a statement of that dualism which, as a statement, would be at once precise and yet without prejudice to any of the rival theories. "Mind your head" is the result of that search. It is the conventional warning in English buses and trams. In its three words the duality and the unity of a man are neatly and correctly indicated. To each of us comes this admonition: mind—your—head. The body of a man is definitely different from his mind, his mind from his body, both are his, and he is not two, but just himself, one. He is to mind his head. Only as we recognize and accept the genuine reality of the mind and the equally genuine but different reality of the body, do all the theories have a subject matter. Only as we recognize and accept the genuine unity of these different realities do these theories have a common problem. That goes for all three theories. I am prepared to consider diverse solutions, including my own, but they must be solutions, not dissolutions. A theory which dissolves the mind in the body so that I am body, but not really mind; a theory which dissolves the body in the mind so that I am mind, but not really body; a theory which dissolves my oneness so that I am body and mind, but not really one—any such theory, no matter how neat and nice, is simply not about me. Perhaps I am insoluble. That remains to be seen. But it is better to be insoluble than to be dissolved. That is my first preliminary consideration.

My second preliminary consideration derives from the peculiar status of the rival theories. A persistent problem is the normal focus for a group of rival theories. But in this case the solutions in all their diversity seem to be as stable as the problem. It seems to be accepted that Naturalism, Idealism, and Dualism together exhaust the field of contenders for the answer to the problem of the unity in duality of man's nature; and at present these three seem also to have exhausted each other. It is this situation which makes some people think the affair is a bogus problem on which no further energy should be wasted. Others incline to the view that this stalemate is waiting for the discovery of new facts which, when obtained, will of themselves establish a definite solution to our problem. I can find no evidence to support that hope. Some people, indeed, are excited by the discovery that when a man thinks, variations in electric current occur in his brain. But such discoveries are like the earlier one, that when a man thinks, even though he does not speak, there are muscular activities in or near his throat. These discoveries add nothing to our understanding of the mind-body problem, they merely illustrate it. In any case, I, myself, have no new facts to report, facts discovered by recent, original research. I do have something significant to say. If I can say it properly, it will be sufficient to restore to Dualism and Interaction the scientific respectability and philosophic integrity they merit. If I make no converts, I may invigorate the faint-hearted. Yet what I have to say will not be conclusive. Were I an Idealist or a Naturalist, I would be, mutatis mutandis, in the same case. Hence in arguing for Dualism, or for either of its rivals, there should be no evasion of this specific question: How is it that these diverse theories about a common problem continue to be significant yet inclusive? In particular, as an exponent of Dualism, I accept responsibility for indicating some of its deficiencies.

Finally I have some remarks to make about language. A rose, we are told, by any other name would smell as sweet. I agree that so it would. Yet when for some time roses have been called by that name, and noses by this other name, to say of my love that she is like a red, red nose, misleads people no matter how sweet she in fact is. It misleads even philosophers, for they, too, are swayed by the connotation of terms. This cannot be eliminated; but a stiff warning given at the right time can reduce the evil consequences. A stiff warning is needed here. The conventional name of each of the three rival theories carries a misleading connotation. The connotation of Interaction is that two or more things of the same order of being mutually operated on each Bother with the same mode of action. Hence to speak of the interaction of mind and body suggests that both have the same kind of being, and that they push and shove each other around. This is hardly the appropriate connotation for the theory which affirms mind and body to be substantially diverse, and the mode of their mutual influence on each other to be proper to that diversity. The connotation is not appropriate, but it is in its way benevolent: Interaction as a name means well. But the connotations of Idealism and Naturalism are malignant. To conjoin by suggestion devotion to the good with disparagement of the reality of the body, as often happens when the word "Idealism" is used, is an unwarranted insult to both. Worst of all is the name Naturalism. Naturalism in our present context names one theory among others about a common set of factual data. Yet as a name, Naturalism carries the connotation of being in accord with nature and holding fast to empirical data, sticking to the facts. Whatever is contrary to Naturalism is by this connotation imputed to be contrary to nature, unempirical, at odds with the facts, hostile to science, and addicted to the supernatural. The result is considerable confusion, and one and only one thing is clear. Naturalism with that connotation is a question-begging epithet. We can not have a fruitful discussion of man's essential nature unless right from the start we recognize and accept without qualification that Idealism, Dualism, and Naturalism are equally theories and in the same sense. Each is an interpretation of data. "Empirical" means attending to and using what can be observed. "Nature" has a number of meanings, each proper in its own context, and none of these is invidious. "Nature" may properly mean the kind of being which members of a species have in common. It may also mean collectively the entire realm of worldly existence, with man either specifically excluded or included. This last may involve a difference not merely of usage but of doctrine. But as regards the three theories here considered, no one has a monopoly of observation, or any pre-eminent claim to being natural or empirical. The intent of Idealism is surely to present an account of man which will be true of his nature and of the facts of his activity. The intent of Naturalism is surely to achieve a rational interpretation of the data of human experience. What is said of each could be said of the other, and also of Dualism. In terms of their intentional meaning Naturalism, Idealism, and Dualism are established terms, each with a distinctive reference. Each has a connotation also which is proper and legitimate. But when innuendos are made along the line of being scientific, miraculous, empirical, supernatural, and so on, each of these theories can and should claim its rightful status as a theory—a sustained, deliberate endeavor to interpret adequately and significantly the data commonly available to all of them, and each should disdain the use of question-begging epithets and disparaging adjectives. That is their status. Performance is another matter. That is what I am now to attempt—performance. There judgment comes after the event and always has a specific reference. By this time we are all familiar with the word Semantics. Let us heed one thing it has to tell us—the warning against being beguiled by words. Having been warned, we should be ready and able to use words with a fair degree of precision and clarity. This is my third and final preliminary consideration.


When one refers to the naive, the ordinary, the common-sense view of man, this may be done either in the way of disparagement or praise. The praise seems to spring from the curious notion that ideas are more likely to be correct when they are formed before much attention has been given to them; the disparagement seems to spring from the opposite but equally curious notion that knowledge obtained at first glance and without reflection must be wrong. Depending on which alternative is taken, advocates of philosophic theories like to stress on behalf of their chosen theory either its basic agreement with common-sense or its essential divergence. I shall do neither of these things on behalf of Dualism. For the virtue of common sense is neither its correctness nor its error, but that it is the source of data unbiased by interest in a theory. Common-sense may be mistaken or correct, it may have prejudices; but it is, as regards philosophic theories, disinterested. This is not because common-sense has no theories, in fact it uses many, but because it is not aware of them. Hence each use, each interpretation of experience, is ad hoc, made or seized upon for the occasion. As a result of this, Dualism, Idealism, Naturalism can each go to common-sense for support and find it. Common-sense dualism is readily illustrated. Why did Epicurus, the Hedonist, take such pains to prove that death ends all?

Because of the wide-spread notion that man is in this life a union of body and soul, that these realities are not only distinct but separable, and that therefore one, the soul, may continue to live after the death of the other, the body. Among what people was this notion prevalent? They were neither savages nor Christians. They were pagan Greeks, common-sense dualists. I do not offer this as evidence in support of Dualism. But if either Idealism or Naturalism ventures to deny that common-sense is on occasion dualistic, they must then reckon with those Greeks. For myself, I shall make no further reference to common-sense as regards argument, but I shall, as need, arises, use it as a source of raw material.

The dualism of common-sense is opportunist and ad hoc. The Dualism I represent is a deliberately fashioned theory about the essential nature of man. It asserts that man is best understood as a unity of at least two diverse natures, commonly denoted as matter and mind, body and soul, body and spirit. I say at least two, because the diversity which requires the rejection of ontological monism seems at times to be inadequately interpreted by a simple dualism. That is one reason why, in stating Dualism, the name for one component is more constant in meaning and less variable in word than is the case with the other. There is, of course, a variation in the terms 'matter' and 'body,' and it is possible that some Naturalists prefer the term 'energy' to name the basic reality from which, as they believe, man and all else have come to be. But these terms, although not synonyms, belong to a group expressive of one kind of being. The variation expressed in the terms mind, soul and spirit rests upon less definite distinctions and may involve basic differences of being.1

1 In an essay published some years ago, Louis T. Moore argued persuasively for three distinct and irreducible forms of being: Three Realms of Knowledge, The Hibbert Journal, Vol. 37, No. 2, pp. 271-290.

For the purpose of this essay, however, I consider only a dualism, using the terms mind and soul indifferently to name one component, matter and body the other. I shall contend that the basis and the justification of Dualism is the knowledge of nature and of man provided by science, philosophy, and ordinary experience. I do not resort to Dualism in order to defend a primitive animism or a traditional religion against the destructive implications of science. On the contrary it is in large measure what science tells us which requires a dualistic theory for adequate interpretation.

Before I proceed further, however, a prevalent disposition to misread evidence in this area needs to be noted, explained, and, if possible, corrected. There is in both common sense and science a notable imbalance in the quantitative distribution of our knowledge as regards the kinds of objects known. We know far more bodies than we do minds, and we know far more about these bodies than about the minds. Quantity all too frequently overwhelms us, and the sheer bulk of our knowledge of matter is at times too much for us. We then forget that we know anything at all of minds, or we succumb to the suggestion that because that knowledge is little, the thing known is unimportant, a mere appendage of bodies. The corrective for such errors is just that firm, direct attention which sees that they are errors, for they arise not from formal mistakes in reasoning but from unchecked and unexamined promptings of many sorts and sources.

Standard usage gives to the words matter and body a fairly constant, common reference, and at the same time differentiates them. 'Matter' names in a generic sense that of which all bodies are composed, and 'body' names the particular forms in which matter is organized. Hence we rarely use the plural form of 'matter,' at least in a material sense, while we often use the plural form 'bodies.' Physics, Chemistry, Astronomy, Geology, and so on, Physiology and Zoology, unite in giving knowledge of matter and of bodies. These sciences are diverse, they also are in part the same. For what one science tells, another science accepts and uses to the extent that the subject matter of the one reappears in the subject matter of the other. And what is present in all is matter and bodies. I am not a scientist, that is, I am not a physicist, nor a chemist. But I have listened attentively to what the sciences say. In what follows I aim to be an accurate reporter as well as a competent theorist. If I fall into error, I shall welcome and readily accept authentic correction. There is no suggestion of scepticism or suspicion in this; my position is that what science tells us about bodies and matter is true. Finally, what I have to report holds for matter and bodies whether matter is taken to be atoms or energy.

Our knowledge of matter and bodies includes on the positive side these essentials:

(1) Being in space: The description of a body properly includes its position. This is generally accepted, but in microscopic physics a limiting condition is encountered. The Heisenberg uncertainty principle tells us that for certain particles, notably electrons, we cannot know both their position and their motion. Any method used to determine the one, excludes learning the other. It is then argued by strict adherents of the operational theory of meaning that those particles for the determination of whose position there is no available procedure, have in consequence no position at all. They are in fact nowhere. A dialectical reply is to ask for the operation which determines that, i.e., their being nowhere. It is also appropriate to repeat the tart comment of a physicist of a different persuasion, "God knows what Bridgman can't discover." In any case these niceties of theory do not establish the sundering of any body from space. The alleged place-less particles have momentum, and that involves reference to space. The original statement stands: in the description of a body, reference to space is essentially relevant.

(2) Quantitative determination: Whether we are dealing with bodies, matter, or energy, quantity is an essential aspect of being and of activity. Units of measure may be arbitrary, but measurement is not, for it is the nature of matter to be "so much," of energy to do "this much."

(3) Causal relations are quantitatively stated in equations. The use of the idea of causality may be objected to, but the crucial term is not 'causal' but 'equation.' Personally I am convinced that scientists use causality whatever they may say, but in any case, they describe activities in terms of quantities and relate them in equations. The activity of bodies—or of energy—in a limited region is formulated in an equation. Within local systems changes, displacements, transformations are balanced out as losses here, gains there: the reduction of gasoline in the fuel tank is equated with motion of the car, heat, and so on. When a rise of energy is noted in a local system as a whole, an outside source is sought; when a loss is noted, escape to the outside is traced. It is frequently difficult to establish the specific equation for a particular situation, and there are doubts as to whether the law of the conservation of energy applies to the totality of local systems, if there is such a totality. But these practical difficulties and ultimate doubts do not concern us here. The essential point is that as regards ordinary, determinable interactions, for a gain here, there must be a loss there, for a loss, a gain. In the language of philosophy and common sense, causation is efficient and requires a transfer of energy; and the transfers balance out in losses and gains.

(4) The unity of a body is the organization of parts in space. This type of unity leaves the parts external to each other. Hence the common type of change in a body is change in size. When additional matter is brought within the spatial organization of a body, that body gets bigger; when some part is removed from the spatial organization, the body gets smaller. It is this which enable us to cut a body, as we say, in two, and get two bodies, each of which is as definitely a body as the original. Cutting in two a body which is also an organism may destroy the organism. But there are still two bodies. If there is an ultimate, literal atom, an uncutable one, its unity cannot be the organization of parts in space, for the hypothesis is that this literal atom has no parts. Are we to say, then, that it is a unit but has no unity? Atomic fission may yield a transformation of matter into energy and instead of an increase in the number of bodies, there is not even one. But after we have recognized and considered these peculiar cases, actual or imaginary, the original statement about the unity of bodies still holds for all others, and these are both the typical and the most numerous. It is more pertinent to point out that the structure or power which maintains the unity of ordinary material bodies is not fully understood. Even so, the unity which is maintained is correctly described as the organization of parts in space.

(5) Identity is identity of sameness. As often as I have had the real opportunity, that is, as often as I have found a scientist who was at once eminent, able to understand my question, and willing to hear and to answer, I have asked this question: If it were possible to identify a specific electron, found when it was relatively by itself, and then to identify it again, after it had entered into many and varied combinations and from these returned again to being relatively by itself, what would its condition be? Invariably the answer is this: that electron would be precisely what it had been when first identified. To my question there is an objection of the type already encountered, because no operation can be specified for performing the hypothetical identification, the question is meaningless. But even from those who thus object, I readily obtain agreement that for any electron—or proton or neutron—it is irrelevant to speak of its having profited by the 'experience' of belonging to this organization or to that. If an electron, then just an electron, no more and no less.

In addition to these five positive statements, there are some truths about matter and bodies which are properly presented in negative form. I shall indicate these by letters.

(a) Matter is indifferent to Time. Strictly, matter and bodies have no history; this present body may be a product of changes in the past, changes in bodies, but the past is not incorporated in the present body: the body is composed of parts and the past is not a part. We use time to determine certain aspects of bodies, e.g., velocity. But before and after have no distinctive meaning for bodies; in fact, they are interchangeable, since all equations can be read in both directions, and all changes are in principle reversible.

(b) Matter is inert and so are bodies. Quick denials of this are usually withdrawn upon reflection. For to say that matter is inert is not to deny motion or energy. It is to deny that any bit of matter, any body, ever of itself does anything different. "Every body continues in its state of rest or motion in a right line unless acted upon by an external force." The key word in this classic formula is "external." Modern physics offers, as near as I can discover, only apparent, not genuine, exceptions. There is a change not made by external forces: bodies left to themselves can lose energy. But there is a limit even to this: there must be inequality of distribution. The grim picture of a universe dead because its energy is evently distributed is familiar to us all. I think it is justified to call energy itself inert.

(c) Matter and bodies of themselves never act for the sake of an end. Final causation has no residence in matter. This has been said so often and with such emphasis by science that it should by now be understood and not questioned. But today there are those who do not like the result. There is, for example, Professor Gotshalk. He first affirms what I have just said, that the findings of the natural sciences eliminate teleology. He then says this is a pity, because it is so depressing. Finally, as a remedy for the depression he proposes that teleology be re-established in things. How is this to be done? By discovering that bodies actually do things on purpose? Certainty not, for they don't. But specific bodies in motion have a "specific matter-of-fact directionality"—and this he proposes to "call their telic factor."2

2Gotshalk: "A Suggestion for Naturalists," The Journal of Philosophy, Vol. XLV No. 1, Jan. 1948, pp. 6-12.

Bodies in motion now have a new name. Call their direction in motion their 'telic' factor if you please, but they still do not do things on purpose.

To these eight truths about matter and bodies, others could be easily added, and some substitutions or subtractions could be made without serious loss. For I have aimed not at a complete account, not at a formally perfect definition, but at an account which is representative of our present knowledge of the essential nature of matter and of bodies. In this I think I have succeeded. We now have before us a fair sample of the truth about what matter and bodies essentially are. Matter and bodies, however, are not themselves before us; a part of the truth about them is. That is the point. Those statements are knowledge.

For the moment let us not consider the source of this knowledge, but rather what can be said of it now that we have it. Can we say of knowledge what was said of matter? Matter has spatial position. Has knowledge? No; knowledge has no spatial position. This is true not secundum quid but simpliciter. We do not fail in assigning a position in space to knowledge because of any breakdown or defect in our methods for locating it; we never fail to spot knowledge correctly in one place because it has just left for another place. It is even misleading to say knowledge is nowhere. The only correct and proper thing to say in this context is that spatial position is not relevant to knowledge. Knowledge exists, but not in space.

Books, of course, do have spatial position. Books are bodies. But while in a figure of speech we say books are full of knowledge, strictly books qua bodies neither are knowledge nor contain it. When a book drops from the table to the floor, knowledge does not suffer a bad fall; when some one gets knowledge from a book, he does not move the knowledge from one place to another; no one examining a book returned by a friend exclaims, 'the rascal, he has taken away some of the knowledge from my book—I wonder where he has put it?' Knowledge is not in space.

That is a negative characterization. A positive characterization of Knowledge is that it is true or false. Those who shy at saying of knowledge that it is false, can substitute the term misknowledge. Or I can use a circumlocution and say, judgments taken distributively are true or false, and true judgments taken collectively constitute knowledge. In any case, true and false are in this context significant terms. But true and false are never properly applied to bodies. A body has position, energy and so on, but is neither true nor false. Nor is any attribute, activity, or relation of a body true or false. True and false are as irrelevant to bodies as spatial position is to knowledge. The conclusion is really a pearl of the pellucid: Knowledge is not body, not an attribute, nor an activity, nor a relation of body. Knowledge is, inter alia, of, that is, about bodies, but their modes of existence are disparate.

To establish this conclusion I have given an argument. It can be summarized in two syllogisms, both in the second figure, Camestres. But some may distrust argument, preferring to put their confidence in experiments. Such persons can be accommodated. Let a storeroom be stored with bodies, of any and every sort that can be found. For completeness let there be a man in the store room reading a book, and let there be a sign above him with this legend in gold, "Science is Knowledge." Now let scientists be equipped with every instrument of investigation, the largest telescope, the most powerful microscope, the most potent cyclotron, the fastest centrifuge, and if there be any other instruments, let them be added. Thus equipped, the scientists are given these instructions: Describe every body in the store room in the terms proper to your science and in no others. Who then will discover there is knowledge in the room? And one or more should, if knowledge is a body or an attribute, relation, or activity of bodies. Who will describe as true, the legend in gold, "Science is Knowledge?"

Will it be the Physicist? No. The Chemist? No. The Geologist? No. Who, then, if anyone? This experiment has, in effect, been done and the outcome is conclusive. One scientist, knowing what it was all about, including the fact that in the room there was a man reading a book, a man in the very act of getting knowledge, went right to work on that man. This scientist was a Behaviorist Psychologist. What did he describe? A behavior pattern. And he claimed the prize, for there was a prize, for having described knowledge in bodily terms. But he did not get the prize. His description was excellent, precise, quantitative, and so on. Its defect was that it was a description of a body's behavior. Of course it was. And he asserted the behavior was knowledge. But when he was asked for evidence, he could give none. He could only shout, 'but I know it is knowledge,' and when he shouted very loud, he was removed to have his behavior studied by another Psychologist of the same persuasion. He was judged to be suffering from an occupational disease called relapsus introspectionis. But not even the Behaviorist read the sign. The Physicist described its golden glitter; the Chemist discovered that in this case, what glittered was gold; the botanist found traces of fossil plants in the gold leaf; but no scientist read the legend, let alone described it as true. Each was exclusively intent on describing bodies.

We now have an important question on our hands. If knowledge does not exist in the realm of matter, what is its mode of being? Is it a natural object with independent existence? I have no desire to seem coy, and the answer, of course, is that minds produce knowledge and possess it. There is no question about that. But there is a question about minds. Are they bodies? Or if not bodies, are they attributes, relations, results, activities of bodies? As regards knowledge, minds both get it and communicate it. In both cases minds are active. What happens when a mind knows something, let it be a body? What most concerns us is that when a mind knows a body, no alteration results in the body that is known. It was Woodbridge, if my memory is correct, who stated this point with perfect precision. Empirical investigation discloses that just as it is the nature of digestion to alter what it digests, so it is the nature of knowing to leave unaltered what it knows. The facts are clear, and as stated. Personally, I can find no excuse for the confusion which is offered as a denial of the plain facts. Certainly in order to enable me to know a body, I often manipulate the body, but the manipulation is not the knowing: I turn a coin over to learn its date; the turning over alters the spatial situation of the body; the learning the date qua learning does not alter the date on the coin. A good thing, too, that it does not; for altering the date of a coin is a crime. Again, it is certainly the case that physical action, altering the body known, often occurs as the result of the knowing; but again it is not the knowing which alters the body, but the action of another sort, which is consequent to the knowing. I look at a man and know him to be the man whose face I dislike; I then hit him and alter his face. But it is the blow of my fist which alters his face, not my knowing it. In fact, after it has been altered, a further cognition may occur; I now like it even less, and I decide to leave a bad job alone. Knowing is an activity, it can be directed on bodies, yet it leaves them as they are.

The case of communication is equally distinctive. We who are teachers are expected to communicate knowledge to our students. They gain. What happens to us? We get tired, for we lose energy in the process; teaching is work. But what happens to our knowledge? Do we lose knowledge in proportion to what we communicate? We certainly do not. We increase our own knowledge in the process of giving some of it to others. In the interaction of bodies, energy is, at most, conserved. In the interaction of minds, knowledge is increased. Matter and mind are essentially disparate in their modes of being and of action.

I listed eight essential characteristics of matter, and with reference to the first and the third, I have presented evidence showing that what matter is, mind is not. I shall now more briefly indicate the results when bodies and minds are compared with reference to the remaining six characteristics As I do this, I urge my readers not to attend merely to what I say, but to allow it to lead them to examine what they already know, and to make comparisons and to draw conclusions for themselves.

Consider quantitative determination. We regularly measure bodies. What about minds? Do we know the length, breadth, depth of any mind. Its weight or mass? Its velocity? These are standard quantitative determinations of bodies. If the mind were also a body, at least one of these dimensions would pertain to it. But none does. The phrase 'mental measurements' is, as I well know, in common use, and a person's I.Q. is stated in figures. But it is also regularly admitted by Psychologists that in no case do these numbers represent direct measurement of the mind or of intelligence. A man can learn to count his ideas, and others can count the results of his mind's activity, his wrong answers to their questions, for example. The electric current in his brain can be measured when he thinks. But the mind itself is never counted or measured. It has no parts, it has no extent or mass. The category of quantity is simply not appropriate to mind.

The unity of a body is organization of parts in space. A mind is not in space, has no parts, and its unity is not organization of parts in space. Does any one really doubt that? Let him try cutting a mind in two. Or let him try to take one part from one mind, another from another, another from another and then try to compose a new mind by putting these parts into spatial adjacency to each other. If the parts fail to stick, can heat be applied until the parts become sufficiently fluid to flow together? Is that sort of process the basis for saying of a man that he has a fluid mind? Finally, the identity of the individual mind is not identity of sameness, but identity persisting through constant change. Every experience changes the mind which has it, yet the mind continues to be identically one and itself.

Thus far, starting with positive characteristics of bodies, emphasis has been on what minds are not. The complementary contrast is obtained when we start with what bodies are not. They are indifferent to time. But minds live in time, incorporating the past in the present, apprehending the future on the basis of past and present, and this living in time is never reversible. A man can walk through a house, retrace his steps, and go out by the door he came in, but for his mind the going back is not simply the original experience in reverse, it is the re-experience of the earlier, first experience. And as we so easily and so truly say, seeing things a second time makes such a difference.

Matter in motion or at rest is itself inert. Minds are essentially active. They initiate action of themselves. Past experience is the chief resource of a mind initiating new activity, and the range of what a mind can do is both limited and indicated by the resources at its disposal. But whereas in the case of bodies, antecedent conditions determine subsequent action, in the case of minds antecedent conditions provide the range and resources for choice. Matter is the realm of necessity, mind is the realm of freedom. This contrast leads us to the next, that between efficient and final causation. It is now accepted that matter has no purposes of its own and that in their interactions with each other bodies display efficient causation only. The prima face presence of purpose in the activity of minds is also beyond question. But there is disagreement over whether minds really and truly act for the sake of an end, or only seem to do so. It is contended by some that both the action done, and that it seems to be done on purpose, for it must not be forgotten that the "seeming" is certainly there and must be accounted for, are in fact the effects of purely efficient, nonpurposive causes. Now it is one thing that man may be mistaken as to his actual purpose and as to the actual causes operative in a particular undertaking, it is quite another that in every case his sense of purpose is completely illusory. Further, the truth of the first is not evidence for the truth of the second. And if purpose is illusory, how does precisely that illusion come into being? Beyond these observations I shall say nothing to persuade anyone that on occasion men genuinely act on purpose. Let them regard themselves and their fellow men. If what they can observe does not establish the fact, then argument is not likely to be effective, not even the argument that they themselves are arguing deliberately and for an end. But there is another aspect of this general situation to which I wish to direct attention. It is the conjunction in one world of active, purposeful minds, and energetic yet inert, purposeless matter. That matter has no purposes of its own does not mean it cannot be used in purposive activity. Quite the contrary. The effectiveness of man's purposive activity in the physical world is crucially conditioned by the absence of purpose in matter. Abundant energy, acting in regular accord to laws of efficient causation, is ideally adapted to purposive direction by minds. If matter in motion started having ends of its own and acting to achieve them, our present subjection of the physical environment to our purposes would certainly be upset. The steady flow of electricity through wires to give me light as I work on this essay, is at once a witness to mechanical law in matter, purpose in man, and the availability of purposeless matter to purposeful mind.

I submit that the more precisely we attend to what we know of bodies and of minds, both to the knowledge provided by science, and that provided by our own ordinary experience, the clearer it becomes that we are confronted by a dualism of substances. When I attend firmly to what I know of a stone and what I know of me, each taken in its concrete particularity, then that they are different in kind is the inescapable conclusion. I commend that procedure to others. It is when I relax, allow myself the lazy luxury of vagueness, and beguile myself with such phrases as 'electricity is potentially life,' and 'ideas are very complex organizations of pathways of nervous impulse in the cortex,' it is then that a materialistic monism acquires momentary plausibility. Idealism, too, can be made plausible by prolonged stress on what things mean, and evasion of the question of what they are. Neither of these monisms can endure the testing of direct observation, pertinent experiment, and precise knowledge. Dualism can. At the same time, as was noted above, one feature of our knowledge makes it easy to succumb to a defeatist attitude as to the reality of minds. We know of bodies which are just bodies. There are many such bodies, and the extent of our knowledge of such bodies is enormous. We know of minds only in conjunction with bodies. Relatively speaking, the bodies conjoined to minds are few, and our knowledge of them is not extensive. So we have this situation. We know a great deal about bodies; and about many bodies, about most of the known bodies, what we know is the essential truth. It is then tempting to try to make out that the distinctive features of living bodies are somehow merely complications of what is characteristic of just bodies. Of the living bodies, a few, relatively, are conjoined with minds. It is again tempting to make out that these minds are just complications of the complication already alleged to be all that life is. After all, minds are so few; it is large numbers which impress us. It is tempting, both reductions are tempting, and succumbing to the one makes it easier to yield to the other. But the affirmation of error does not change the facts. It often provokes from others the assertion of a counter error. Thus Idealism evokes Materialism and Naturalism, and vice versa. The distinctive merit of Dualism in this situation is not its elegance as a theory—it lacks that grace—, but its refusal to deny, suppress, or pervert facts in order to simplify and sustain a theory. It accepts the facts and then as best it can develops a theory to interpret them. Matter and Mind are declared to be each real in existence, each irreducible to the other, each with a distinctive nature, because a careful examination and comparison of what we know of them both, discloses that such they are. That is my case for Dualism.


Before taking up the specific topic of this section, it may be well to consider certain objections which have probably been building up in the minds of philosophically experienced readers. One objection is almost certainly directed against my use of 'substance.' In modern times such withering assaults have been made on this category that it may seem an inexcusable ignorance or a worse folly to go on using the term as if it were in good standing. If I insist on substance, why have I not supported the use with explanation and argument? Another objection may have been provoked by my failure even to mention recent discussions by other philosophers of the general subject of this essay. Why have I not noted and welcomed such support as may be found in the writings of Professor Ducasse? Why have I not replied to the arguments against Dualism which are presented by Professor Ryle?

I am aware that thus far I have done none of these things. I do not intend to do them now. But I shall try in a few sentences to justify my procedure by explaining it. The criticisms of 'substance' are of the category itself, and a sound defense must in like manner be of the generic notion. But in this essay I am not concerned with that general problem, but with Matter and Mind, their essential differences, their relations to each other, and so on. It is true that, as regards the general problem of substance, I am convinced that the category is well grounded and that the arguments against it have clarified rather than invalidated its meaning and use. Hence in presenting my case for Dualism I have assumed the category and offered evidence that, given the category, Mind and Matter are different substances. No doubt the attempt to do that, so far as it is successful, is also evidence that substance itself is a valid notion. Yet the difference remains between the two problems. The discussion of substance falls outside the proper scope of this essay and I shall leave it there.

A reply to objections of the second sort can be made along similar lines. The statement, examination, and criticism of the views of such distinguished thinkers as those I have mentioned, are major undertakings in each case, and merit and require independent essays. But I wish to state in addition a different and, I think, a more important explanation of my procedure. Attacks on Dualism are in these days more frequent than defenses of it. But if Dualism can be sustained, that must be possible by exhibiting Dualism directly, together with the evidence which supports it. Arguments against the arguments against Dualism are on occasion needed. There is also the need, as great if not greater, for the simple presentation of a case for Dualism, without the complications and diversions of replies to the arguments of its opponents. Dualism, I think, finds its best defense in itself, and that is the procedure followed in this essay.

We now return to our main theme and take up the particular doctrine called Interaction of Body and Mind. The primary reference of this doctrine is to a familiar, readily observed pattern of human life, the constant response, of mind to body, body to mind. As a theory, Interaction is at first little more than the assertion that what we take to be the mutual interaction of mind and body is just that. All the immediately relevant facts confirm the theory; I know of none which is at variance with it. Even those who, because of their adherence to other theories, deny that the facts are what they commonly are taken to be, rely on interaction in practice. The Idealist takes thought for his body; the Naturalist drinks a cocktail to put his mind at ease; and the special Semanticist who identifies meaning with bodily response, expects to be understood. Were I reading this essay aloud to a group of listeners, what would I and they be doing? I would be communicating ideas to them. How? By direct thought transference? No. I would make noises, specific sequences of particular sounds, enunciating them as clearly and distinctly as possible. It is those sounds which would reach the ears of my listeners, or, if one prefers, certain vibrations of air would reach their ears. And eventually their minds would receive the ideas. Where the instrument of transmission is writing, printing, and reading, the basic pattern is the same, only the details are more complex. Those are the facts; they are what Interaction denotes.

There are no facts in this field which challenge Interaction. But other theories, developed in other fields to interpret facts of a different sort, have implications which appear as objections to Interaction. It is important that this be understood. The psychologist, notably the experimental psychologist, is a Dualist by inheritance and an Interactionist in practice. If the psyche had not been regarded as a distinct kind of being, Psychology as an independent science would not have been begun. If he did not rely on interaction, the experimentalist would never ask his subjects to cooperate and to make reports. It is not in Psychology, but in other sciences, even in metaphysics, that we first find enunciated such principles and theories as 'entities are not to be multiplied beyond necessity,' 'final causes are as sterile as virgins dedicated to God,' 'multiple observation is the test for reality,' and so on. These theories in the fields of their origin and initial application are substantiated by their fruits. A notable exception may well be the principle of economy called Ockham's razor, since, as was noted centuries ago, however useful economy may be to man, it may not be a regulative principle for either nature or God. In any case, these theories arose outside Psychology and said nothing directly about interaction of mind and body. It is only when they are generalized and then extended to Psychology, that they are found to involve objections to the independent reality of mind and to interaction.

A careful observer, for example, would not fail to report the presence of purpose in human activity, and anyone who doubted this finding, would then not be given argument but would be referred to the facts. Yet purpose in human behavior is often denied, and the avoidance of teleological terms in psychological explanation is today commonly regarded as scientifically desirable. The explanation of this is a matter of record. In the history of the physical sciences we can read that progress in precise knowledge and the elimination of teleology went on together. What brings success stimulates imitation. Procedures and principles highly successful in the physical sciences have been generalized and set up as standards for scientific method in general, and then applied to different sorts of subject matter. When this produces clashes, as it certainly does in Psychology, between the imported ideas and those developed directly from the native subject matter, the latter have often been condemned simply on the basis of the alleged universal standards of scientific method. This is not sound empiricism, but it is not done completely without reason. That last sentence needs to be noted and remembered in the case of Interaction, for the objections to Interaction are largely reasons and not facts. That is why these objections require such careful consideration, instead of just summary disposal by confrontation with the relevant facts. But in giving them serious consideration we should not forget their origin, nor be taken in by their resilience, their ability to return in full vigor after what seems a conclusive disposal. Objections to Interaction are properly met by the facts of Interaction. But the origin of these objections is not within the domain of human behavior, but outside it, and this origin is thus untouched by the evidence Interaction presents. Flourishing, non-teleological physical sciences, and man's desire for simplicity and uniformity will together regularly produce objections to Dualism and Interaction. In favorable soil error, as well as truth, when crushed to earth, will rise again. It is still error.

Several of the more common objections to Interaction were examined in an article in Mind and I shall not repeat that examination here.3

3 Second Thoughts on Causation, Dualism, and Interaction Mind, LVI., N.S., No. 221.

Its conclusion is that in this case, as in all other cases of causation, no objections based either on the nature of the things involved, or on our ignorance of how interaction occurs, are valid. Hume proved that. In questions of causation, the prior question is not how, but simply is—is there causal action?

Granted that this is the correct question and that the initial reading of the facts says that causation occurs, it is still possible that the answer called Interaction is mistaken. The general principle of the conservation of energy may be open to doubt, but when we are dealing with particular bodies, we know what it takes for one body to do something to another body, and we know that the mind does not have that. Energy is required and the mind lacks it. Again, we know what happens when one body does effect another, the first loses energy. But the body loses no energy in its relations with the mind. Therefore, there can be no interaction. I accept the whole argument, but only and precisely in its own terms. Note what they are. Here Interaction is taken to be energy exchange, what one body does to another body. But the mind is not another body, nor the body another mind. Neither one pushes the other around, as if both were bodies; neither one communicates ideas to the other, as if both were minds. What would a body do with an idea, suppose it got one? Or the mind with motion if it got some? Like the dead atheist prepared for burial, all dressed up and no place to go, the mind, having acquired velocity, would still have no destination. What happens when mind and body interact is this: to a specific state of the body, probably a specific state of a specific part of the body, the brain, and a state proper to that part, the mind responds with a change proper to it, an idea, a feeling, a perception, as the case may be. This response is determinate: the mind feels what the body determines. On other occasions, to a specific state of mind, a state proper to the mind, let it be a specific intent of will, the body responds in a manner proper to it, the body moves. This response is also determinate: the body does what the mind wills. This is control, in both directions, without exchange. That is why I use the term response. This, I affirm, is an accurate, although general, description of what happens when I will to speak, and do speak; when vibrations reach the ears of those who hear, and their minds then receive ideas. It is a description which deliberately employs terms developed, some by common sense, some by the special sciences, including psychology. The result, I claim, is an account true to the facts as we now observe and understand them. It is an account which is verified by the facts it claims to describe. Is it alleged that only a few bodies are capable of such a special activity as I have called response to mind? The allegation is correct. Only bodies conjoined to minds display this response. But the point is not, how few are such bodies, but that those few do respond. An angelic intelligence might allege that very few minds have this peculiar capacity of responding to bodies. He might be right. There may be far more angels than men. But relative rarity is no evidence for non-existence.

This modifies the traditional doctrine of Interaction, and requires that we accept in both mind and body a capacity beyond those ordinarily credited to them. Further this capacity functions, so far as the evidence goes, only in a specific situation, the union of body and mind in one being. What valid general objection can there be to this? If it be urged that in all our knowledge of just bodies, there is not the slightest hint of this capacity to respond to a mind, I grant the contention. It would be odd were it otherwise. I can also easily imagine the incredulity of a couple of pure intelligences were they told that some minds had the capacity to respond to bodies. They might say with complete truth that in all their knowledge of pure intelligences there was not the slightest hint of any such capacity. But we are not pure intelligences. Neither are we mere bodies. We are minds and bodies united in single beings. It is clear, at least to me, that what we can learn of minds and bodies in that union, should be conclusive as to what each can do in that union. It is true that we have considerable knowledge of what just bodies can do. But it is simply fatuous to take the activity of body in isolation from mind as exhaustive of what body can do in union with mind. What can properly be required on the basis of the reliability of scientific knowledge is that when a distinctive activity is offered as part of an interpretation of a special situation, this new activity shall be a coherent addition to, not a contravention of, what is already known. The type of response I have described meets this requirement. The nature of matter as previously established and the laws of its behavior are not violated. In its response to mind, the body is not required to think, to give up energy to a non-body, or to receive energy from such a source. Nor is the body required, as it is in Naturalism, to create a diverse and extensive range of new entities, such as sensations, feelings, volitions, thoughts, personal unity, and all the rest of what are then called mental phenomena. In the theory I am describing and defending, the body does not make ideas nor does the mind create physical energy. In each case that which responds does so in terms of its own resources. In the body mind relation what is distinctive is the relation itself, the unity, including mutual response, of two diverse substances in a common life.

It should also be noted that this type of interaction is not committed to a one-one correspondence of brain state and mental state. What is asserted is that to some activities of the mind there are responses of the body, to some activities of the body there are responses of the mind. But response is not correspondence, and some is not all. The emphasis on "some" merits a word of further explanation, for it is peculiar to Dualism. According to Naturalism not all but only some states of the body are accompanied by and are determinant of mental phenomena; but all mental states have a basis in the body. Idealism reverses this, claiming that all "material" objects exist only as derivatives from mind, while only some ideas have these material derivatives. The possible exceptions, panpsychism as a form of Naturalism, and some versions of absolute Idealism, do not invalidate this general contrast. But Dualism holds to "some" for both sides of the relation; and it is only "some" which is warranted by the available evidence. It seems equally unlikely that we shall ever be able to determine by competent evidence whether or not there are psychic correlates for all the bodily changes of which we ourselves are not conscious, or somatic correlates for all the psychic contents of the unconscious.

This is an appropriate place to consider an objection to which it may seem I have made myself particularly vulnerable. As definitive of the nature of matter, I have used what physics tells us; as definitive of the nature of mind, I have relied upon man's first hand knowledge of himself. It can be objected that these sources cannot be conclusive since they deal with their respective subjects at the extremes, so to speak, of unrelatedness. My own words can then be cited against me: "it is simply fatuous to take the activity of body in isolation from mind as exhaustive of what body can do in union with mind." Had I earlier followed my own admonition, this objection continues, I would have studied mind and matter as they actually function together; I would have listened to physiology and neurology rather than to physics, to animal psychology and Behaviorism rather than to introspection; and I would have reached the solid ground of modern naturalism rather than the quagmire of dualism.

The objection is plausible. It seems to be a specific and valid application of the general principle of empiricism, namely, that to determine what matter and mind are and can do, they should be studied, without pre-judgment determined by theory, in their experienced actuality. There is no disagreement between me and my critics over this principle. It is in the application, in the practice of the principle, that disagreements arise. In developing my case for Dualism have I lived up to this principle, or have I violated it, in contrast to the advocates of Naturalism, who really exemplify it? That is a fair question, and to it a reply must be given.

It is a fair question, but its formulation is open to the charge of being question begging. To say that we should learn what matter and mind are by studying them in their functioning together, is in words to assume the very dualism which is one of the chief points at issue. This situation was recognized, and I trust, fairly resolved at the beginning of this essay in the first of the Preliminary Considerations. But opponents of Dualism and Interaction need on occasion to be reminded that it is experience, not theory, which initially presents dualism and interaction, that monisms, naturalistic and idealistic alike, initially appear as theories challenging experience. I do not hold that against them, I am no naive believer in "sticking to the facts of experience," with no recourse to theory; but it is well to keep the record straight. The particular question, then, that is before us can be stated as follows: the data provided by what man is and does are of two sorts in their initial presentation; the problem for theory is how these diverse kinds of data are to be interpreted; and in that context the question arises, are we to use as our criteria of the nature of matter and the nature of mind, criteria determined antecedently to this specific, present problem and by the use of other data, or criteria developed directly from the data now before us? Or, more briefly and as a direct challenge to Dualism, does not the principle of empiricism require us to accept what man is and does as indicative of the nature of matter? From the behavior of the electron to the behavior of man, do we not obtain in a hierarchial order the evidence of what matter can do at different levels of organization? If this approach is maintained, the objection to Dualism continues, there is no occasion for claiming to find in man evidence for a new and different substance, for what man does, including all the so-called mental phenomena, demonstrates what matter, at that high level of organization, can do.

This is a very neat begging of the question; but neat as it is, it does not unambiguously provide a materialistic monism. One can with equal ease and justification alter one word, and then in the name of empiricism an idealistic monism is established. Like this: the principle of empiricism requires us to accept that mind can do all that man does, for what man in fact does is the demonstration of what mind, with the high power of externalization found in man, can do. The entire physical world, empirically found always as an object of human perception, thus becomes existentially dependent upon mind, and the obdurate objectivity of what are called material things, becomes a quality given them by mind to facilitate not only scientific study, but esthetic contemplation and enjoyment. When properly stated, Idealism acquires a really astonishing plausibility!

It should now be clear that the admonitory advice given to Dualism, be empirical, study man in his concrete actuality and accept what you find, is followed by Naturalism in a strictly one way fashion. This is also the practice of Idealism, although it moves in the opposite direction. But the case of Naturalism is the more significant, for its pretensions to empiricism are more vigorously made and more widely accepted. Matter and mind in their functional unity are the declared object of investigation, but the approach of Naturalism is always from matter, as source, to mind, as derivative. Naturalism first learns of matter from the physicist, not from the psychologist, just as Dualism does. If subsequently there is what seems to be an open-minded readiness to accept on the basis of the facts of human activity unexpected and unique capacities in matter, this readiness is really necessitated by the firm determination of Naturalism to maintain the primacy of matter. The modern exponents of Naturalism are notable for their tenacious and frequently ingenious efforts to reach by their chosen route what is distinctive in mind, and to preserve the integrity of mind against reduction to what they themselves call the crude materialism of the nineteenth century. But the primacy of matter is always affirmed and never compromised. The strength of this approach, and that strength is very great, comes largely from the fact that before mind is even encountered, the reality and general nature of matter are securely established. Whatever we may think of mind and before we think of it, we are certain about rocks. Rocks are matter, not mind. So are hydrocarbons, electrons, and lots of other things. The reality of matter and the variety of its forms and activities being firmly, independently, and antecedently established, the problem of man is taken up; and, in the name of empiricism, the concept of matter is enlarged just enough to encompass in principle the new features found in psychic activity.4

4 The successes and failures of Naturalism are not here being considered in detail, for I am concerned with the positive presentation of Dualism, not with a critical examination of either of its rivals. The constant internal threat to Naturalism is, of course, that its every apparent success in assimilating mind to matter turns out in fact to be a reduction. A careful consideration of this aspect of Naturalism can be found in A. Campbell Garnett: Naturalism and the Concept of Matter and A Naturalistic Interpretation of Mind, Journal of Philosophy, XLV, No. 18, pp. 477-489, 589-603.

In this situation my precise dissent from Naturalism is that I do not accept independence and priority in time as equivalent to metaphysical primacy: that the sciences provide a history of the world according to which the material order existed before the animal, and the animal before the human, does not establish the ontological priority of matter or even its independence of mind. But I do agree with the methodology of Naturalism as regards formulating a concept of matter; I also practice it; in fact I practice it as regards the concept of mind. And that is the point at issue in these paragraphs. The charge against my procedure was that in my dualistic interpretation of man I relied upon criteria of matter and mind derived from other sources than the empirical unity of mind and matter as they are found in man. It is characteristic of Naturalism to make this criticism. My reply thus far has been to make plain that the practice of Naturalism itself as regards its initial and basic concept of matter is precisely that, and with good reason. The clearest and most reliable source of knowledge of the nature of matter is matter itself, unambiguously and unconditionally itself. It is thus that the Physicist studies it. That is why I listen to him as to a reliable authority. So do the advocates of Naturalism. We agree in our practice, and I say we are right in what we do. For the same reason I would follow the same practice in learning the nature of mind—I would if I could. If I could bring under direct study unambiguous cases of pure intelligences, existing and acting independently of matter, I would certainly do so, and I would there obtain my basic criteria of the nature of mind. This would greatly strengthen the case for Dualism! Lacking such data, I use the best available, those provided by introspection. Here the concurrent existence of the brain, a material thing, may be fact, but I can at least attend exclusively to the mental data, and learn something of the nature of mind from what the mind shows itself to be. In this I am at least emulating what the physicist does when he studies matter. When he studies matter, the concurrent existence of himself as an observing mind, is certainly a fact, but he attends exclusively to the physical data in order to learn what they are. Both of us encounter difficulties, but these do not invalidate either our aims or our methods.

Thus equipped I have taken up the problem of the nature of man. Here data are complex, prima facie of two orders, yet in specific cases often ambiguous. Here one is constantly involved in the complementary processes of interpreting data to determine their nature, and determining their nature in order to know how to interpret them. Having in hand criteria, antecedently formulated, for two orders of being, matter and mind, one is prepared to give to these data a provisional but systematic order. Something of this sort is used by all advocates of Naturalism who recognize that the nature of man is a peculiar problem. But when these criteria for mind and matter are not only antecedently formulated but also weighted, so that one is accepted as a criterion of the real, the other of merely the phenomenal, then the metaphysical question has been settled prior to the consideration of some of the most significant evidence. On the other hand, because one enters this problem equipped with concepts of matter and mind regarded as having equal metaphysical standing, it does not follow that one must leave it with Dualism and Interaction as the solution. It means that the metaphysical decision is stated but not yet decided. Within the problem both concepts are properly subject to modification as well as testing. Eventual decision as to dualism or monism and if the latter, which type, or to a neutralism or something else, rests with the adequacy and inadequacy of the various theories to relate and interpret their common data. This is good procedure. It is neither becoming nor necessary for me to claim I have followed it, for the evidence on that point as well as the conclusions I reached are now before the reader.

But even as a convinced Dualist I find the situation complex and puzzling. Not all minds seem to be of the same order. Do dogs also exemplify Dualism and Interaction? Is mind continuous with life? If not, is mere life an unusual form of body activity? Is it an incipient mind? Or, as the late Dean More argued in the essay already cited, is life in itself a distinct kind of reality, irreducible either to body or to mind? I do not know the answers to these questions. But I do not propose to let my ignorance of some things make me deny what I know of others.

What astonishes me is our inattention to what is often plainly before us. Consider, for example, the machines popularly called lie detectors, and let us examine not their rare failures but their normal successes. These instruments vary in what they directly measure, and most of them measure a number of things. But in every case what is measured is strictly physiological, blood pressure, rate of breathing, and so on. Yet a lie simply cannot be defined in bodily terms. A lie is the deliberate assertion as true of something known to be false, with the intent to deceive. The point of this definition is not its formal perfection—it may well be imperfect—but that it makes clear that what a lie is, is intelligible only in terms of will, knowledge, purpose, and the distinction between truth and falsehood. None of these is body, energy, or motion, or attribute or relation of them. Blood pressure is. A person can decide in his mind to lie and require his body to speak the lie, and it does. What he cannot do is suppress the body's own response to the presence of the lie in the mind. I have been told, as a correction, that the variation in blood pressure is response not to the lie, but to the emotional tension which accompanies a lie and also certain other things. This bears upon the accuracy of these machines for detecting lies and lies only. If the emotions which affect blood pressure can occur in other situations, then the reliability of the machine for indicating lying is reduced. But as regards response of mind to body and body to mind, and not their identity, it confirms what I have already said.

As always in this problem, we are brought back to the question of actual occurrence. Can I think and then speak? Can I decide and then act? Is my body touched and do I then feel? Does light reach my eyes and do I then see? I can and I do. I find interaction, this mutual response of mind to body, body to mind, to be fact.


Thus far I have been concerned with demonstrating that Dualism and Interaction together provide the best interpretation at present available of the nature of man. This theory recognizes and preserves the genuine diversity of mind and body, confounding neither with the other, and presents them in their functional unity. Dualism is in this notably superior to both Idealism and Naturalism, and the more it is regarded in comparison with them, the better it looks. Yet I do not myself regard Dualism as a completely adequate theory of the nature of man. In this final section I wish to indicate what I think is the chief defect in the theory which I accept and uphold.

When I attend as persistently and comprehensively as I can to what I myself am, I then find Dualism defective in its account of my unity. But this defect is not the one with which Dualism in this respect is usually charged. The usual criticism is that having distinguished mind and body, Dualism then separates them so that they cannot ever do anything together. This is to charge Dualism with not providing for interaction, and that is not true. Functional unity is provided. What is lacking is an adequate account of man's essential unity. How is man both two natures and yet one person? How in this one person are both mind and body united so that this person is genuinely one? Even this is but a one-sided statement of the problem. For what needs explanation is that the unity of the person is both more complete and pervasive than can be accounted for by a functional union of two natures, and also in other aspects so loose that the de facto conjunction of its diverse components seems not only accidental but irrelevant. Examples of that complete, mutual involvement of body and mind will presently be studied in some detail; the other aspect, the loose, irrelevant conjunction can easily be illustrated. Think how often we observe some of our own bodily motions as though they were those of a detached and foreign thing! The jerk of the loosely swinging leg, for example, when the knee-cap is struck lightly with a hammer. Yet of the jerk, we are also conscious: that which we observe with detachment, we feel intimately. By means of the fluroscope, on the other hand, we can observe motions in the body of which we have no direct awareness whatever. But that which we observe and feel, and that which we observe and do not feel, seem equally irrelevant to the life of the mind.

In situations of this sort, other theories seem to me to be even less illuminating than Dualism, but that does not make Dualism itself adequate. Dualism preserves the integrity of the mind against reduction to a by-product of the body. Dualism preserves the integrity of body. Dualism provides for the interaction of mind and body. All this accords with the facts. The body has a being of its own, the being proper to a body. The mind has a life of its own, the life proper to a mind. Each contributes to the life of the other. But the life of the mind, including interaction with the body, is not the whole of what my personal life actually is. In my actual life, the fact that I am an embodied mind gives to that life experiences and qualities it could never have, were it a mind which merely used a body. The clearest illustration is provided by feeling. Most of my feelings, feelings experienced in consciousness, are of the body in their content. Love, for example, is or can be in man an activity of the mind as well as of the body. When it is that, the body is incorporated into that activity. The body is then more than an instrument. In love the body contributes itself, the mind itself, and the result is not merely a functional interaction, it is an infusion of the mind with the Me of the body. A further and more specific illustration is provided by that ingenious machine, already mentioned, the lie detector. It is to be remembered that the basis of this machine is the correlation not of two things but of three, physiological changes, lying, and emotion. Emotion is the middle term. Emotional tension is responsive to truth telling and to lying; blood pressure and other similar activities of the body are responsive to variations in emotion. Now lying is definable and intelligible exclusively in terms appropriate to the mind; blood pressure in terms exclusively appropriate to the body. That a pure intelligence had no body would not, so far as I can see, render it incapable of lying. That a pure body had no entanglement with a mind would not, so far as I can see, render it incapable of having blood pressure with variations. But emotion? Could either a pure intelligence or a pure body shudder?— "tremble convulsively with fear, horror, or aversion?" Could either a body or a mind by itself laugh? These are not interactions of two components, not a constant conjunction of two components. The shuddering, the convulsive trembling with fear, is one in its own essence, and that which alone can shudder, the embodied soul, is one. The lie detector discloses, to return to that illustration, both the interaction of a dualism and a unity which transcends interaction.

But there is a further difficulty. For in addition to this genuine synthesis in the person of body and mind, diversity and disparateness are also genuine and persistent. What really happens when, as we say, we grow old? The body as a body changes but does not age. Every change in the body simply as body could be reversed. But the living body does age. It withers, and falters in function. What happens to the mind? The mind does not age, it matures. The maturing mind and the ageing body are, if I may use a figure of speech, moving away from each other. Yet in the maturing of this diverging mind the emotional experience of the person is an essential ingredient, and it is the embodied mind which feels. The substantial unity of a person is not simple in itself, nor yet simply a unity. Mind and body in man are both united and not united.

I find my understanding of this situation and hence also my exposition of it, very unsatisfactory. I find the unity of man in some aspects beyond comprehension. I can recognize it. I can do a bit more. I can see that the incorporation of the body and the mind into the life of the person occurs on the side of the mind, not of the body. The body has no mental life; it is the mind which has a bodily life. But what is that unity? How is it to be adequately described? I do not know. With reference to these facts, poetry and religion seem to do better than does philosophy. They never let lack of explanation deter them in the assertion of essential truths. Orthodox Christianity, for example, unabashed by either physics or metaphysics, calmly asserts the resurrection of the body, and the life everlasting. But the body is to be transfigured. The nonsense which philosophers and theologians have developed starting from this article of the Creed, should not blind us to the fact that the Creed in this displays how firm is its grasp of the genuine unity of mind and body in the person. By contrast, Dualism on this point is dumb. That is its deficiency. It is a serious one. Yet for that deficiency I at present see no remedy in philosophy. Fortunately, however, the deficiency in theory is precisely that and nothing more. Dualism is defective in its theory. Man is not correspondingly defective in fact. But he is baffling.