organizations realize antithetical principles; the one achieves freedom, the other necessity. The notion of means involves rigid determinism,-a means which is not the necessary means is not a means; the notion of end involves freedom,—a necessary end is not an end. The dichotomy itself is grounded in necessity. It is because the principles are antithetical that each must organize itself independently of the other. There is no common quality of mind and body and no common measure between them, which would render it conceivable that mental things and bodily things should enter indifferently into either a mental or a bodily process. Equally inconceivable is a mind without embodiment, and a body without mind to give purposiveness to its co-ordinated processes. It is only as whole and individual, and not as composed of classes of discrete entities, that mind and body are in perfect union in a relation of absolute mutual interdependence.

The term which seems to me best adapted to express the interaction of the mind and the body is solidarity. The old legal meaning of this word exactly fits the notion. It was originally a term of Roman and Civil law to express the character of a contract which, in a single matter, involved individual obligations on the part of the contractors severally, with corresponding rights to the holders. The term solidarity means, therefore, that diverse, even divergent, activities together bring to pass a single common result to which all the activities contribute without sacrificing their individual integrity. The term causality, on the other hand, as used in physical science (apart from any question as to the legitimacy of its employment therein) means that in some way something which is distinguished as cause disappears, and its exact equivalent reappears in something which is distinguished as effect. The interaction of mind and body is not of a causal but of a solidary nature.

I can now, I think, make clear my scheme of this interaction. Let us call living action A, then we may say that every A is B C, these standing respectively for what pertains to the mind system and to the body system. B and C are not in direct relation but only in indirect relation. A B is

different from A C, and the relation between B and C is that both are implied in A. Thus there is interaction between B and C without causal relation. For, let us suppose that the initiation of a change is in B, the change is a change of A, but A is also C, and therefore there is a change in C consequent on the change in B. It is the nature of the consequence which is all-important in my theory. A is always changing, change being of the essence of activity, and the change of A is a change in system B, and a change in system C. The relation of B and C to one another is · mutual adaptation. A profound change in B may necessitate very slight adaptation in C, may conceivably necessitate no adaptation at all, and then the changes in B and C are quite disproportionate. It is this that differentiates my view from parallelism. The change in the mind is never commensurate with the change in the body, and there is no one-to-one correspondence which would make it possible for even an infinite intelligence to read the one in the other.

Let me try and apply the formula. Life, I have said, is enduring and efficient, and I have shown that these characters are antithetical. I suppose, then, life to exist as an undifferentiated unity. If I am challenged to justify this supposal by any actual experience, I have, of course, to acknowledge that there is no such experience. I am presenting a scheme of the genesis of experience, not a temporal history of it. There is no experience of life save as already differentiated into body and mind. This is not a difficulty peculiar to philosophy, it is an inherent difficulty of all scientific explanation. How, for example, can I schematize what light is without the notion of latent energy, yet, so far as experience is concerned, latent energy is non-existent energy? I conceive life, then, as first an undifferentiated unity which to realize itself, to become actual, to be living action, must differentiate itself. This differentiation is a dichotomy, a separation into two individual systems, the order of which is governed by principles which are opposite and contradictory, but at the same time the systems are complementary. One principle is realized in the mind, the

other in the body. One forms an enduring agent preserving past and projecting future action, and the other an efficient instrument inserted into the whole system of interacting forces within which it is operative. Freedom is essential to the agent, mechanical necessity to the instrument. Here we must be on our guard lest our metaphors defeat us. Agent and instrument are metaphors which almost directly suggest the distinction between a machine and its function, and we cannot apply this distinction to the relation of mind and body. Between life and function there exists no distinction. The body is not like a motor car which a man leaves in his garage until he has need of it. Living action progresses with the continuous modification of mind and body. The action is neither physical nor psychical nor partly physical, partly psychical, it is psycho-physical. No physical influence affects the mind save through the body, and no psychical influence passes from the mind save through the body. All and every experience modifies both mind and body, but the modification is not a mechanical addition to something which but for the addition remains identical with what it was before. However subtle and imperceptible the change may be which new experience effects on the mind, it is the whole mind which is changed. And however slight the demand on the body a new experience makes, even though the action called for may appear a mere repetition of countless previous similar actions, a change is effected in the whole disposition of the co-ordinated mechanisms which comprise the body. We know that the organs of the body and the constituent elements of the organs atrophy with disuse and grow with use. A continuity of change in mind and body is a condition of life.

Here I may offer a remark on the bearing of this theory on the question of survival. It is not strictly relevant, yet to many the predominant interest of the whole problem of the interaction of mind and body is the light it throws on it. I see nothing irrational in the notion of a survival of personal experience after death. The credibility of it, as matter of fact, must depend on ordinary scientific evidence,

and with this my theory has nothing to do. The only question it is concerned with is how far the system I call mind is conceivable when the system I call body is practically destroyed. There are two types of religious dogma; one is the natural immortality of the soul, the other is the resurrection of the body. I do not propose to discuss or compare them in regard to their conceivability, for with the first my present argument is not concerned. I will only point out, therefore, that so far as the view of the relation of mind and body which I have tried to set forth is concerned, some embodiment is essential to every presentation of mind as image of a concrete person, or as general idea or concept of an actual individual. If, then, we believe that the departed soul can or does return now and here, or that it may or will return hereafter, or that it moves to a new sphere and lives in other conditions, the pertinent questions in regard to any such belief are those which St. Paul set himself to answer: "How are the dead raised up »? And with what body do they come?" A soul without a body would be a non-receptive, non-active mind, and that is only not a contradiction in terms because there are no terms to contradict.

Mind and body are then, in my view, two disparate but not separate nor separable systems or orders. They are the necessary condition of the realization of life in action. They arise and undergo modification continuously in the progress of living action. They interact continuously by mutual adaptation. They are never in direct causal relation, in the sense in which that relation holds in an energetical system, but they have a common source and co-operate in a common end.

CHAPTER IX

THE MECHANISM OF PSYCHO-PHYSICAL ACTIVITY

Une sensation renferme telle ou telle idée: donc nous avons ces idées aussitôt que nous avons cette sensation. Voilà une conclusion que les mauvais métaphysiciens ne manquent jamais de tirer.-CONDILLAC, Traité des Sensations, Bk. I. chap. ii. sect. 8.

WHEN Hume described the constituent elements of experience as impressions and ideas, and when Kant described the fundamental matter distinct from the form of experience as the manifold of sense, they referred, not to what we call perceptions, but to something simpler and more elementary, to what we call sensations. The pure empiricist, that is, one who acknowledges experience as the only criterion of reality, seems to find in sensations not only something indisputable, simple and elementary, but also something which in a singularly precise way corresponds to the functions of the constituent elements of the neural structures of the body. In fact, when we begin our study of the mind by making an inventory and descriptive classification of the sensations we seem to be following a natural course, directly suggested and borne out by the science of the structure and function of the nervous system. Up to a certain point everything has seemed to confirm this view. It has always been recognized, and the recognition is the starting-point of a science of psychology, that sensation is sui generis. It is impossible to identify it with physical structure, with vibration, material or ethereal, or with any kind of mechanical action, yet there has seemed to be in fact a relation between the two not only in their simple origin but at every stage of their growing complexity. This parallelism of