Chapter 3

How animal movements arise

1822. According to my theory of animal instinct, there are as it were two spheres of phenomena, one subjective, the other extrasubjective. In other words, we have a sphere of feelings and a sphere of external movements. The first sphere prompts the second: movements are produced by feelings. Feelings contain the cause, which is entirely subjective; movements contain the effect which is entirely extrasubjective.(13)

1823. Body is a substance but, as term of the sensitive principle, occasions subjective phenomena or feelings. As sensiferous, that is, as a foreign force changing the term of feeling, it occasions extrasubjective phenomena or movements and their thrust. But because the substance of body is one, there is no repugnance in conceiving the soul, which has some influence on the subjective body in so far as this is term of the soul's feeling, as necessarily productive of extrasubjective phenomena in the body. Relative to substance, the subjective and extrasubjective body is the same.

1824. Thus, the influence of the soul on the body, the power that a simple spirit has of putting a body into movement, loses much of the mystery associated with it. There is no difficulty in conceiving a soul which, active in its own feeling, does not emerge from it. Feeling, too, is something simple and incorporeal. But I do not posit any power in the soul other than that which the soul unfolds within the limits of its feeling. This power cannot be denied in the soul's regard because continual experience shows that the soul modifies its own feeling with its own energy. Analysing this feeling, I found it to be the thalamus in which an extended element is joined to a simple element. Moreover, I discovered that the extended element, which constitutes the necessary term of feeling, is itself a substance. As such it is not only the term of feeling, but is operative in its own way even outside feeling where it appears as a force foreign to feeling, a force which changes the term of feeling and consequently acquires the two names, matter and body. It is now clear why the number of subjective phenomena correspond with the number of extrasubjective phenomena, and vice-versa. It is clear that the soul, without emerging from its own feeling, but operating solely on its term, can determine a body to change place, that is, to move.

1825. Note that the way in which the soul moves the body consists in arousing movement in a way entirely different from impulses and every other mechanical communication of motion. The difference is immense and, we may add, infinite. For the sake of brevity I will indicate only two of these differences:

1. Mechanical communication is limited to the communication of a quantity of motion which already exists, and no more. The soul, however, produces and, as it were, creates motion to which quantity is unassignable. Motion is as great as the activity of the soul on its own feeling, an activity that can be increased or diminished at every instance.

2. Mechanical communication is limited to successive communication of motion, which passes from one molecule of a body to another. The body is propelled or attracted at various times and as parts of the body oscillate. Sometimes a break is made in the cohesion of the parts; again, the continuity of communication can cease when, for example, cohesion is at a low level as in fluids, or when cohesion is destroyed by violence which shatters the body, and so on. The impression of motion coming from the soul, however, in so far as motion is restricted to the extended element, the term of feeling, is simultaneous in the entire extended element in which the soul intends to operate. Consequently, the parts of this extended element are neither separated nor disconnected, but can be moved as the soul pleases. This is true both of fluids and of solids (the extrasubjective forms of the term). It occurs, moreover, without our being able to assign a precise limit to the quantity of motion which the soul is impressing.

1826. Careful consideration of these things will show how greatly the explanation of phenomena gains as a result of the discovery of this totally non-mechanical way in which the soul arouses and creates motion in the term of its own feeling, and consequently in the extrasubjective body. So far, every known way of communication is entirely insufficient to explain how the soul, through instinct or will, can move the members of its own body. Take, for example, the weights carried by a porter or the efforts made by an athlete. How is it that muscles are so powerfully contracted or distended that bones obey them and help them to press, push, attract, throw, and in a word conquer enormous resistances. According to physiologists, the will initiates its movements in the brain.
But can the brain, a very soft substance, be a firm point on which to rest a lever?
Is the brain a point of resistance which serves to originate mechanically the stupendous power shown in arms and legs?
If the soul impresses movement on the encephalic substance, and it is this quantity of movement which must be communicated through the nerves to the muscles and then through the muscles to the joints (as mechanical motion is communicated), will the desired effect take place? The soft substance of the brain cannot be excited beyond a minimum quantity of motion which is mechanically incommunicable to more resistant parts.

The phenomenon we have to explain, however, presents an extremely noticeable quantity of motion. If the minimum quantity of motion supposed in the very tender substance of the brain were the same kind as that shared through great effort by the nerves and muscles, it would have to increase as it made its journey. In any mechanical communication, however, motion would necessarily diminish as a result of various resistances and finally be altogether extinguished. There is, therefore, no hope of explaining through mechanical laws the movement which the soul impresses on the members of the body. But in the theory I have explained, every difficulty ceases. According to this theory, the soul exercises its power over the extended element which is the term of its feeling. It does this simultaneously in all the parts of the feeling in which it acts. This action is efficacious, but not according to any determined measure. The modification it produces is not necessarily in the same direction or in a straight line. It can have the form and, as it were, the mark which the soul prefers and can change at will. Consequently all the necessary multiple, various, powerful, circular movements can appear in the extrasubjective order. They are in fact manifested when we move our own body for different reasons, as common experience testifies.

1827. Various explanations have been attempted: attracting forces, electricity, magnetism, and so on. But the instinctive or voluntary movements of various members of the body do not in any way obey the laws according to which these agents move when left to themselves. It is true that when such agents are considered as servants of the soul, they can be thought of as used in part by the soul, but the soul does not take the initiative in their use. Moreover, whatever aspect we consider, difficulties would be multiplied instead of decreasing. We would still be left with two questions: 1. how can the soul make its dominant motor- power felt by these agents? 2. how can these agents communicate to the members the power of a soul which can will or not will, and from one moment to the next command the most complicated, contrary motions? Even to explain the first of these two questions, it would be necessary to recur to the efficacy possessed by the soul within the sphere of the subjective order, a sphere from which it does not emerge. But electric, magnetic, etc., phenomena belong solely to the extrasubjective order. The question in this case would remain as it was; it would not be solved except by having recourse to the theory I have proposed.

Notes

(13) There is an apparent contradiction here with what I have said several times elsewhere, that is, subjective and extrasubjective animal phenomena have no mutual likeness, but only some kind of mutual proportion. They cannot, therefore, be considered as causes and effects, but simply as two orders of parallel phenomena. And it is indeed impossible to find any kind of likeness between feelings and bodily movements. Here, on the contrary, I have maintained that feelings are the cause of movements, and reciprocally that movements excite feelings. I need, therefore, to explain my concept better and thus resolve the contradiction which it could present to the spirit.In my opinion, feeling alone, or that vital principle which lies in the feeling of the actuated continuum, is the true, active animal principle. Now, when the internal animal feeling changes, there are also changes in the movements of the animated body. These movements, recognised by us through our external sensory organs, are represented as sensations in these organs. We have, therefore, a class of sense-experiences whose true cause is our sensory which, however, is passive relative to an unknown agent represented to us by the sense-experiences themselves. Consequently, feelings are the Scholastics' equivocal causes of movements. Such causes are neither immediate nor full, and not even true causes. Nevertheless, they act, and an effect follows on their actions. For example, one could say that the sun is the cause of the plants and flowers which it helps to produce by moving their immediate causes, and thus contributing something along with them to the production of plants and flowers.