Chapter 11

Propagation of the movement stimulated by the rational principle
and beginning in the body; the parts to which it spreads

365. From what has been said, we note:

1. The rational principle acts on the sensitive-corporeal principle.
2. It exercises this action in two ways: through the understanding or intellective sense and through the will.
3. Because the understanding is a passive and necessary power, and the will an active power, the intellective soul influences corporeal life in two ways, one necessary and one willed.

366. 4. It is no surprise therefore that physiologists distinguish two orders of nerves and muscles, voluntary and involuntary, and that the nerves are sometimes moved in two ways, voluntarily and involuntarily. In fact, I think it probable that all the nerves are subject to the power of the will,(159) although its control varies in proportion to our need to subject them to our will, and to their distance from the place (the brain) where our will directly operates by means of images, as we shall explain.(160)

367. We need to see where rational activity produces bodily movements directly. Is it in the nervous system alone or elsewhere as well, and does the nervous system itself communicate to other parts the movement it has received?

368. In the second case, the other parts of the body would not be connected to the soul but would simply be under its influence by means of genuinely animated nerves, which are the true seat of the soul. At the very least, the instinctive, sensitive principle would not be in those parts or connected to the rational soul.

369. To answer this question we must first distinguish between the soul's action on the body and the manifestation of this action through movements which can fall under our external senses and thus clearly reveal the action.
I have not always held the same opinion on the matter. My present opinion is that the rational soul probably acts in varying degree on all parts of the living body; the fundamental feeling of continuity, together with its sentient principle, is present in all parts. But either because a suitable organism is lacking or because of opposing forces, the feeling is not suited to direct stimulation by the soul in every part of the body. Consequently the feeling of stimulation is either totally absent or extremely weak and limited.

370. By feeling of stimulation I mean the organic movement suitable for producing a sense-experience.

371. This kind of feeling must be granted to the fundamental feeling itself, because in a living animal there is continuous movement (of physical continuity), which ceaselessly stimulates the feeling(161).

372. We can say therefore that where the fundamental feeling of stimulation is missing, that is, where parts are not susceptible to stimulation by internal, direct movements which produce feeling-experiences, sensitivity is apparently lacking. This seems to me to be the concept we must form of the parts of the human body which we called insensible.

373. According to our supposition, nerves are parts organated in such a way that they can admit the extension, frequency, rapidity and measure of the instinctive movements which generate sense-experience. Hence, although the fundamental feeling of continuity exists throughout the whole fabric of the human body, excitable sensitivity is absent in some parts. These are moved principally by the nerves on which the soul acts most effectively, that is, in pronounced muscular movements, rather than by the soul itself directly. This difference, I repeat, must evidently be attributed to the compact organisation of the body. When the intellective soul exercises its motor action equally on two parts of the body, one part moves incredibly quickly through internal movements, and produces stimulation of feeling or sense-experience; the other part is not susceptible to these wave motions, oscillations, etc. The first part consists of a fibre organated with its fluids to produce such mobility; the second part, which is not so suitably organated, either resists the impulse and causes it to terminate uselessly, or is moved while keeping the same texture in its smallest parts.

374. Granted this, we must say that the movements initiated by the intellectual principle and suitable for being known by us begin in the nerves and, following special laws, spread to the other parts of the human body.

375. But further investigation is still required to find the parts of the nervous system where movements produced by the intellectual principle begin.
The general answer is that they are determined by the nature of the special movements produced by the rational principle. But their general classification can be of two kinds, as follows.

376. We have seen that the rational principle acts in two ways, as instinct and will. Two nervous systems, the ganglionic and the cerebro-spinal, correspond to these two ways in the human body. When the rational principle produces movements by means of the instinct, the ganglionic nervous system is directly affected, but when it produces movements by means of the will, its action is in the cerebro-spinal system. This needs to be explained.

377. The cerebro-spinal nervous system is the instrument of the feelings we have called shaped or surface, that is, external sensations and images. These feelings supply the matter for our knowledge of extrasubjective bodies and their accidents, but they are certainly not knowledge. Although, strictly speaking, they are simply signs of the presence of a body, they are not arbitrary because they contain the action of the body itself.
Feeling is ours, not the agent's, although the agent through its action exists in our feeling, that is, exists in the very same surface space where we feel. This identity of space between the active agent and our passive selves makes us attribute the modification of our feeling to the body as proximate and quasi-formal cause of the modification. In this way the agent, different from us, appears coloured, odorous, etc. The extreme precision of the edges presented by shaped feelings and the amazing differences of the edges provide us with an extraordinary impulse to accept them as qualities of bodies. They thus become matter for our knowledge of corporeal entia.

378. Knowledge always precedes the action of the rational principle because the latter acts only through knowledge. But the knowledge present when the rational principle acts as instinct is not the same as that present when it acts as will. Let us suppose that someone has had some unexpected bad news, the sudden death of a dear relative, for example. He certainly uses his cerebro-spinal nervous system in receiving the sensible signs of the news. Whether he received the information by word of mouth or by letter, the sensations of hearing or of sight would have revealed the sad event to his mind. We can also suppose that the dear departed came to his mind through image-packed memories, although these are not necessary for causing the sudden sorrow. The purely intellectual thought itself, which at that moment hardly had time or will to recall images, is sufficient; it causes the immediate withdrawal of blood to the heart, shown by pallor, reduced pulse, trembling, spasms and even syncope and apoplexy. These effects were not commanded by the will; they did not come from images resident in the cerebro-spinal system; the sole task of the images was to inform the understanding of the event. They came from the information itself given to the understanding. This information did not need to affect the brain beforehand, but immediately communicated its action to the trisplanchnic nervous system which controls the circulation, secretions, passions, that is, unshaped feelings.(162)

379. But this is not the case when we consider movements produced by the intellective principle as will, not as instinct. Whether this principle's act of will is spontaneous or deliberate, 1. it decides to will a particular movement, 2. it decrees this movement and 3. produces it.

380. The intellective principle cannot form the volition or decree pertaining to a particular movement unless it conceives the movement. The conceived movement towards which the will's decree is borne as its object is virtually nothing more than an extrasubjective movement. Only this kind of movement is perceived with distinct, shaped feelings suitable for attracting attention and fixing intellectual perception. On the other hand, it is very difficult to say that the intellect perceives the movement by means of a subjective, prior feeling, because a prior feeling, which is the product of the soul's very own energy, is hardly distinct from the greater feeling pertaining to the total energy of the soul. Only when the total energy passes into act and produces the movement does it distinguish itself by acting and become special energy. If the will therefore produces movements without knowing them, it must produce them, it seems, with the kind of volitions I have called 'purely affective'.(163) But even here the will's participation would be united with the instinct only after the latter had begun the movement and thus rendered distinct the energy of the soul which produces the movement. This energy would be drawn out of the total energy in which it was immersed. Only on this condition can the intellect perceive the separate, limited energy suitable as an object of the will.

381. Leaving aside this extremely obscure mode of the will's action, I shall speak only about volitions whose object are extrasubjective movements which the understanding can distinctly know and perceive. Relative to these volitions, I said that the object of the will, that is, the movement which it decrees, is presented to the intellect by means of images evoked only in the brain, the organ of the imagination. The will desires and decrees to execute this simple or complex movement which it preconceives with the help of the imagination. We need not discuss here the way in which animal forces are usually involved in the determination and execution of this act.

382. The imagination, which pertains to the cerebral system, presents to the understanding the simple or complex movement on which the will deliberates. The will executes its choice with a decree which pertains not to the phantasy but to the intellective, spiritual order. The decree is a practical judgment by which the will agrees that the movement is good and to be carried out. This practical judgment is the start of the act which carries out the movement.

383. How is it carried out? The movements which the rational principle produces as a result of a decree of the will must be distinguished into two classes.
Some movements, but not others, are accompanied either by a sensible, animal pleasure or by the satisfaction of a need. They are desired for the pleasure attached to them or for the need they satisfy. The other class of movements, which lack that pleasure or satisfaction, are not desired in themselves but employed as a means to obtain some good which is properly speaking the object of the volition. For example, human beings have a speech-instinct; the child instinctively repeats the sounds it hears; similarly birds reproduce the song of their species, etc. The movements of the vocal chords satisfy the animal's need and instinct; it seeks pleasure, and escapes the discomfort it would suffer if the instinct were suppressed. On the other hand, when a human being buys a book, the movements performed to obtain it are not the pleasant object in which his will terminates; his aim is possession of the book and the knowledge he hopes to gain from it.

384. The rational principle however proceeds differently when it carries out movements of the first and second class. In the first class, pleasant sense-experience and movement are so united that the former is the proximate energy initiating and producing the movement. The intellective energy need only stimulate and aid the pleasant feeling produced instinctively by the movement.
On the other hand, movements unaccompanied by a pleasant sense-experience must be produced directly by intellective energy not only without the aid of sense-experience but in opposition to it. I can for example move an arm or leg by strength of free will, even though the movement may be accompanied by pain.

All this is confirmed by consciousness.

385. No wise, intelligent person will say that it is unreasonable for us to attempt to deduce some conclusions about animal organism from knowledge of such subjective facts. These conclusions, which cannot be confirmed as demonstrated truths except by the surgeon's knife and physiological thought, concern the famous question mentioned above, the distinction between motor and sensitive nerves. Movements accompanied by sensation and initiated by sensation itself begin, it seems, at the root of the sensitive nerves, which consequently would have the double property of feeling and motion.

On the other hand, the class of movements produced directly by the will's command and without any sense-experience (which is the proximate cause stimulating and producing them), are apparently activated by the motor nerves. These nerves have only the property of movement, not of special feeling. If they do have the property of feeling, it is manifested only on a condition different from the property of the first class. In this case, the rational principle which moves the nerves does not stimulate them to feeling, and the movement given them is not a sensiferous movement.

386. This last hypothesis seems to me most probable and totally in harmony with the special sensibility proper to the cerebro-spinal system. In fact the sensibility of this system in a normal state is revealed only at the two extremities, that is, the external extremities by means of sensations, and the internal extremities by means of images. Hence, no special, distinct feeling is revealed throughout the total length of the nervous filaments. If we suppose that the commanded movement devoid of sense-experience begins precisely where images reside which re-present the movement itself to the intelligence, we immediately see why the movement is communicated from the nerves to the muscles without any sense-experience whatsoever, that is, without a sense-experience which of itself seems to stimulate and produce the movement.

387. Here the difficulty will be raised as to how brute animals, which are totally lacking a rational principle, can produce movements of the second class.
I reply: by means of the unitive force. Animals associate in their imagination movements of the first class with those of the second class. The sensitive principle, stimulated instinctively to produce movements of the first class, also produces those of the second whenever these are necessary for the first, that is, whenever the animal must produce the second in order to procure the sensitive satisfaction it looks for in the first.

388. We can show by another excellent demonstration of the simplicity of the sensitive soul that the second class of movements depends on the cerebro-spinal system or some part of it, and that the first class begins either in the ganglionic system or other parts of the cerebro-spinal system itself. The sensitive soul, seeking to procure the pleasure and avoid the pain connected with the movements of certain nerves, imparts movement to other nerves whose roots differ from those of the first class. But to do this its activity must be contemporaneously present and active in different parts and places. This presupposes that the sensitive soul is immune from the laws of space.

389. I conclude. The rational principle, acting as instinct, exercises a direct action on the ganglionic nervous system; as will, it exercises a direct action on the cerebro-spinal nervous system. Both systems intercommunicate, as anatomists well know: the lateral ganglia of the great sympathetic system have multiple communications with the cerebral and rachidic nerves; the cerebral ganglia communicate with the pneumogastric system.

390. Accurate observation of the accidental differences between these nerve unions found in different individuals could greatly clarify the levels of the will's action, in different people, on the passions and on the movements of so-called organic life.

Notes

(159) For example, Willis' accessory nerve produces instinctive movements, but when used to produce the movements necessary for the voice is clearly subject to the power of the will.

(160) In my opinion, simple psychological observation supplies us with arguments suitable for indicating the internal construction of our body. For example I can apply psychological observation to the question of voluntary and involuntary nerves by noting carefully what happens during convulsions. Convulsive movements certainly suppose a stimulus acting on the nerves, but the person subject to the convulsive movements does not feel the stimulus in any way. The movements arise in him suddenly, without his will and without his feeling their primal origin. We must say therefore: 1. certain nerves can be moved involuntarily; and 2. they give no sensation of the foreign cause or stimulus that moves them. This fact alone demonstrates that there are nerves which are either involuntary or can be moved by a cause foreign to the will. This second alternative seems to be nearer the truth because convulsive movements, when considered individually, can nearly always be carried out by an act of will. Voluntary movements are precisely those where the nerves do not feel a stimulus, as I discussed in paragraphs 346-348.

(161) AMS, 318-322.

(162) The great sympathetic system is certainly not the organ of shaped feelings which pertain to the brain and the spinal chord. It is however the organ and seat of unshaped, diffused feelings.

(163) AMS, 612-635.