Part Five

CHAPTER 3

Origin of the idea of our own body, as distinct from exterior bodies, through the fundamental feeling

692. Bodies exist as substances different from God and ourselves.
As the proximate cause of our sensations their essence consists in a certain energy acting upon us, relative to which we are passive. And any activity, different from our own, constitutes a different existence. Hence Berkeley's error: he denied corporeal substances (cf. 672-686).

But we do not think of body only as a substance causing corporeal sensations. We bestow upon this substance other qualities such as extension, shape, solidity, mobility and divisibility, and generally speaking all the physical and chemical properties that bodies manifest in their relationship to one another and to us. The principal property with which we endow body is its aptitude for life when it correctly unites with spirit (cf. 668-669). We also endow it with the aptitude for modifications which cause it to lose life by separating it from spirit, and for modifications which cause pleasure and pain, sensations of colours, sounds, tastes, and so on.
We have yet to show however how body is known by us as the subject of these properties and capacities. If we succeed in doing this, we shall also be able to explain the ideas of the various qualities attributed to body.
It is clear that, in order to complete our study of the ideas of matter and of body, we are about to enter the wide field of physical nature where we have to deal with life, feeling, and different kinds of sensations .

693. Bodies possess a physical relationship amongst themselves, and a relationship with our spirit. Observation enables us to know the facts constituting and determining these two relationships.
In the physical relationship between bodies observation shows that, when bodies are related to one another locally, various changes take place, according to stable laws. This capacity for receiving modifications or alterations corresponding to their respective positions results in the mechanical, physical and chemical properties of bodies.
But are these properties, such as propulsion, attraction, affinity and so on, true powers of the body in such a way that bodies are the true causes of all the modifications to which bodies are subject?

This question has nothing to do with my argument. I mention it in order that it may not distract the reader if it should occur to him. We are not asking if propulsion, attraction, cohesion, and affinity are true forces; we merely want to know exactly the simple facts presented by attentive observation.(112)

694. All these facts can be reduced to the following formula: 'When bodies are placed in certain positions relative to one another, alterations occur which are constantly the same, given the same bodies and the same positions.'(113) We now ask how we form the ideas of these alterations, ideas presented to our spirit by the alterations.
We conceive mechanical, physical or chemical alteration or change in bodies through their presence in certain positions only in so far as: 1. the modified body acquires a different capacity for acting upon us by causing internal or external sensations different from those caused previously; 2. the modified body acquires a different capacity for modifying another body - in the last analysis, this modification is reduced to the different capacity that the modified body possesses for acting upon us. When a body changes colour, taste, hardness, extension, force, or any of the sensible qualities resulting from a new state, it has changed only its capacity for producing sensations in us.

Only through our senses can we come to know when a body receives or loses some property or power without changing its sensible qualities. If the change were of such a nature that it presented no direct or indirect sign to our senses, we would not perceive it in our feeling, nor could we think, imagine or assert it.(114) If we adhere to pure observation, we have to say that any change in a body must be sensible by our senses in order to be something for us. It must finally produce some effect or action on our senses. Any difference found through such changes on the part of bodies can be reduced to a change only shown directly or indirectly to our senses. If one body changes colour in the presence of another, as grass and leaves become green on contact with the light, that body has suffered a change shown immediately to our senses.

If I magnetize a needle, the change in the needle is not immediately obvious to my senses; neither touch nor sight present any change. Its new properties are shown only by its power to attract other ferrous metal, or to point towards the pole when set on a balance. But seeing the needle act in this way means that I now receive a certain series of sensations I did not possess while the needle remained unmagnetized. As far as I am concerned, the new power acquired by the needle is reduced to certain new capacities for producing different sensations in me. And this is true whenever we examine the effect of one body's action upon another; any changes mentally conceived in a series of bodies acting upon one another effect only their capacities for acting upon us.

Let us imagine that the last of these bodies acts upon us. Through it, and only through it, we know the changes which have taken place in the others. If the series of bodies is called A, B, C, D, E, F, Z, we find that the change suffered by Z, which has affected us, can be defined as follows: 'The change in Z consists in its losing the capacity for producing one series of sensations in us, and acquiring the capacity to produce another series.' I go on to define the change experienced by F as follows: 'The change in F consists in acquiring the capacity for bringing about the change described in Z.' I have experienced the alteration in Z through my senses, but the change in F is known only through that in Z. If I now wish to substitute the known value of Z in the definition of the change in F, I produce an awkward definition, but nevertheless the only one possible: 'The change in F consists in its capacity for producing the change in Z through which Z loses its capacity for producing one series of sensations in me and acquires the capacity for producing another.' In the same way, the change in E can be defined only in relationship to the change in F, and so on, back to A.

Amongst the alterations in all these bodies, only that of Z is known to me of itself. The rest are known as first, second, or third, etc., causes of Z. Everything I know about the properties of bodies to modify one another is reduced to the acquired capacity to modify me. Knowing the modification I experience, I know the capacity producing it in me. Knowing this, I know relatively the causes more or less remote to it.(115)

Our observations show clearly that all mechanical, physical and chemical qualities or properties constituting the relationship of bodies to one another are (when we limit ourselves to observation alone) simply powers capable of modifying us and producing sensations within us.(116) Hence, all the ideas that we have or can have of these properties are reduced to the different impressions the bodies make upon us, and to the different feelings they cause in us. We can mentally conceive only those mechanical, physical and chemical powers of bodies that either modify us, or modify and change the powers to modify us.
Our question, therefore, has been reduced to a careful examination of the relationship of bodies to us as we explain the origin of their sensible qualities, to which all other qualities are finally referred.

695. In speaking of the mutual connection of bodies, I have kept to pure fact and avoided difficult questions. I intend to follow the same method in indicating the connection of bodies with ourselves, and I ask readers to remember that I am confining myself to the limits placed by observation. I mention this to prevent a fruitless search for something not contained in the work.
Observation does, however, take us further in this field than it did when we examined the connection of bodies amongst themselves. We ourselves are one of the terms of the present relationship, and it is obvious that we can observe ourselves more intimately because our consciousness shows us the facts taking place in our spirit. While observation cannot tell us if bodies are the true causes of the modifications discerned in them, we can, given certain relative positions of the bodies in question, distinguish our own actions from other actions by simple observation on ourselves.

696. Observation of the connection of bodies with ourselves offers three distinct relationships which can usefully be indicated here.
The first relationship: an intimate bond between our senseprinciple and a body that becomes its term (matter). This I call life.(117)

The second relationship: a fundamental feeling(118) proceeding from life, that is, from the first bond. Through this feeling, we habitually feel all the material, sensitive parts of our body.(119)
The third relationship: the capacity possessed by the sensitive parts of our body for being modified in certain ways. Various species of external sensations correspond in us to these modifications, and in them the perception of bodies external to our body.

697. The connecting bond between external bodies and ourselves consists, according to the idea we have formed of it, in considering these external bodies as capable of modifying the sensitive parts of our body and providing our spirit with varied sensations.

698. First, I have to clarify the opinions I have proposed, then prove them. To clarify them, I begin by establishing clearly the distinction between life and the habitual, fundamental feeling caused by life.
I said that life was a certain intimate, unique bond of spirit with matter. In this bond, matter becomes the constant term of the sense-principle in such a way that the two things form a single, underlying factor.(120)
Life is not feeling, or at least not feeling as observable by us; feeling is an effect of life. We can see this if we realise that all the parts of our body, provided we are alive and healthy, enjoy a life of their own and are joined to us according to their condition in such a way that this bond is called life. Thus all the animated parts in us carry out the vital acts proper to them, the principal of which are nutrition, heat, and vital movement, which result in incorruption and the capacity of each of the various parts of the body for different functions. But the seat of feeling, as we have seen, is not every part of the body, but only those parts we call nerves. We say this without wishing to enter the physiological field, foreign to our argument.(121)

699. We can usefully employ our imagination to form a clear concept of the sensitive body. Let us picture the human body present to us simply as a network of nerves and bereft of all parts that have no feeling. This is the sensitive body which, when joined to us vitally, enables us to feel. In my opinion, we perceive this body habitually and uniformly with an innate, fundamental feeling which, however, we do not advert to easily because of its continual sameness, although we are aware of the changes that take place as one or other of our nerves is touched. Stimulation of the nerves produces a more marked sensation, easily adverted to because it is unusual, temporary and incomplete, not universal and constant like the first, stable feeling which, diffused throughout the nervous system, often goes unobserved, even by philosophers, because it is con-natural and permanent.

700. We now have to examine in detail: 1. how we feel our sensitive body in which the fundamental feeling is present; and 2. how we perceive external bodies which only touch and stimulate our sensitive body.
Because bodies, as we have said, are perceived by us as substances causing sensations, and as subjects of corporeal qualities, it will help us if we apply what we have noted about the perception of bodies in general, first in a special way to sensitive bodies, and then to sensible, non-sensitive bodies. We can then discuss both kinds considered as subjects of the qualities indicated in them, qualities which are either sensible or reduced to sensible qualities (cf. 693-694).

701. First, I note that our body (and when I speak of our body I always mean the part where we are sensitive) is perceived in two ways.
1. Like every other external body it is perceived by touch and sight or, in a word, by all five sensories. When I perceive my sensitive body as acting on my five organs, I do not perceive it as sharing in sensitivity (this must be clearly understood because of its supreme importance), but as any other external body which, falling under my senses, produces sensations. In this case, one organ of my body perceives another. It is as if someone were to anatomise and perceive the nerves of another living, sensitive ens whose nerves are not sentient to the person anatomizing them, but only to the person to whom they belong.

2. We also perceive our body through the universal, fundamental feeling by which we feel life in us (a feeling witnessed by our consciousness, as we shall see later), and through the modifications experienced by the fundamental feeling itself by means of adventitious, particular sensations.

These two ways of perceiving our sensitive body can be distinguished appropriately enough by the words 'extrasubjective' and 'subjective.' When we perceive our body subjectively, through the fundamental feeling given to us with life itself, we perceive our body as one thing with us. Hence, through its individual union with our spirit, it too becomes part of the sentient subject, and we can truly say that it is felt as co-sentient by us. On the contrary, when we feel our body extrasubjectively, in the way we feel external bodies through our five senses, it is outside the subject, like other bodies, and different from our sensitive powers. We do not feel it as co-sentient, but merely in its external data, in so far as it is capable of being felt. We must take great care to distinguish the subjective from the extrasubjective way of perceiving our body. A great part of what we have to say depends upon this distinction.

702. The subjective way of perceiving our body is twofold. We perceive the sensitive parts of our body subjectively with both the fundamental feeling, of which we have spoken, and with the modifications experienced by this feeling when impressions are made on the nerves.

703. The second, subjective mode of perceiving our body is shown by an accurate analysis of external sensations which reveals two things in every sensation:

1. The change arising in the sensitive, bodily organ which, as a result of the change, is felt differently, that is, the fundamental feeling suffers modification.

2. The sense perception of the external body that has acted upon us.

Let us take the sense of touch as our example. When we rub some rough surface against the back of our hand, we feel two things: the hand and the surface rubbing against the hand. The first is what I have called a modification of the feeling of our body; the second is the sense perception of the rough surface.

704. This twofold quality of sensation must be noted with extreme care. But here it is sufficient to indicate the connection between these inseparable, simultaneous feelings included in the single fact of sensation. What I am saying is this: on the one hand, the feeling that we experience through the simple change(122) occurring in our bodily organ is a modification of our fundamental feeling; on the other, we have a sense perception of an external body accompanying this modification, but altogether different from it. This fact occurs in us on the occasion of the first change and feeling, although we are unable to find a necessary connection of cause and effect between these two things. Nevertheless, as we shall see, we can note the presence of a single cause of both the subjective feeling and the extrasubjective perception experienced in the senses.

705. What do we mean when we say that our first feeling of change in a bodily organ is simply a mode of the fundamental feeling of life through which we feel all the sensitive parts of our body? This feeling begins when life begins and ends with life itself, but what does it enable us to feel? As we have said, the matter of this feeling are the sensitive parts of our body. But when we feel them, it is natural for us to feel them as they are; and if we feel these parts as they are, it follows that we feel them differently when they change their state. The matter of feeling has changed because the state of these sensitive parts has changed.

706. The activity of the fundamental feeling, therefore, is always the same in so far as it is alert to feel the state, whatever it may be, of our sensitive body. Consequently all the changes taking place in our bodily organs must be perceived by us through the act of the primal, fundamental feeling. The act by which the feeling is modified as changes take place in the body constitutes the first of the two elements forming our adventitious sensations which arise when foreign bodies influence our body (here I follow common opinion).

Our body is perceived by one and the same act in two ways, substantially and accidentally. The primal feeling and the change it suffers are two facts from which I conclude that the spirit, on first uniting itself individually with an animal body, must direct its activity in such a way that it mingles, as it were, with the body which it embraces and unceasingly perceives. As long as this vital union endures, the spirit perceives the body in the act and state in which it finds itself. When the body changes through external influence, the sense-activity of the spirit united with the body also undergoes a change of form. The spirit's activity experiences inevitable modification because its matter changes, although without deliberate intervention on its part. It is as though a person finds a scene changing before his eyes not because his glance varies, but because the object of his vision changes. In our case, the act of feeling is the same whether we are dealing with the body's first state, or with all the other acts and states and partial modifications of the sensories that follow the first state.

707. If the nerves possess all the necessary conditions(123) for sensitivity, they feel when suitably touched and affected by external bodies. If we then go on to say that the sensitive faculty of the soul is spread throughout the sensitive body, and that the soul with its power of feeling is therefore present to every part of the body, we are not offering a theory(124) but merely affirming what observation tells us. Because our power of feeling possesses a primal, essential act (the fundamental feeling), extending to all sensitive parts of our body, it is inevitable that this power, or rather the ever-present soul, experiences a disturbance (I mean, undergoes some passive experience) when the sensitive parts of the body are changed through the action of some external body. Perception of this passivity, experienced in a determinate way according to the quality of the sensation, is what I call sense perception of bodies, as I said above (cf. 674).

708. If our previous observations are correct, they show that two different forces affect our spirit. One causes our vital, fundamental feeling; the other modifies and changes the matter of this feeling, producing simultaneously both subjective sensation and bodily perception. According to our definition, the essence of body consists of an action done in us in such a way that we feel ourselves passive relative to the energy perceived intellectually as an ens at work in us but different from us (cf. 674, 684). Experiencing two species of feeling, undergoing two kinds of action, and feeling two sorts of energy, we realise that there are two species of body, our own and external bodies.

The existence of these two kinds of body is proved by the fact of our consciousness, and is as certain as that fact [App., no. 25]. Not even sceptics deny the fact of consciousness. The existence of these two bodies, therefore, is proved by observation, not by reasoning. In the same way, their definition does not exceed the limits of observation because we make it consist in a certain energy(125) which we feel working in us and of which we are conscious that we are not the authors.

709. But because it is difficult to reflect upon the fundamental feeling of our sensitive body, we need some suggestions to help us observe what takes place within us and become aware of this feeling which has escaped observation by so many thinkers. What follows, therefore, is not a proof from principle, but an attempt to make observation easier.

710. First, it is necessary (and we cannot insist sufficiently on this) to distinguish the existence of a feeling within us from our awareness of it. We can indeed experience a sensation or a feeling without reflecting upon it, or being conscious of it, although without reflection and the consciousness resulting from it, we could not affirm, even to ourselves, that we have and experience such a feeling. Indeed, if we did not know how to advert to it, we could happily deny its existence. Leibniz saw this. Locke and many others did not (cf. 288-292). In order to conclude that a feeling was not present in the first moments of my existence it is not sufficient therefore to say: 'I did not notice then, and do not notice now, the universal feeling of my body that you posit.' You could have experienced it, and could be experiencing it now, without paying sufficient attention to advert to it.

Thinkers accustomed to concentrating on what takes place in their consciousness notice matters connected with the human soul that totally escape ordinary, unreflective people. 'Know yourself' is a much-needed reminder of where we normally stand with regard to self-knowledge. It is extremely difficult to discern what really takes place at the source of our passions, where our affections, habitual tendencies, and intentions are rooted. Only those generous enough to pursue virtue with all their mind and heart attain to adequate self-knowledge.
We must insist, therefore, that those who have not yet recognised in themselves the feeling of which we are speaking should focus their attention more carefully and delicately upon themselves rather than reject blindly any notion of the feeling.

But if people have not been able to distinguish between feeling and noticing feeling, they are certainly ignorant of the essential difference between sensation and idea. Sensation can never be aware of itself; the understanding alone is aware of sensation because such awareness is either intellective perception of sensation, or reflection upon intellective perception. The act by which we understand sensation is altogether different from the act of sensation itself, that is, from the act with which we feel. Consequently, if an ens undergoing sensations does not perceive them intellectively, and remains unaware of possessing them, it can never indicate them to others or to itself. This explains why beasts lack the power of speech: they lack reason.

711. On the other hand, it may appear easy to advert to the existence of the fundamental feeling. In this case, there could be danger of mistaking the nature of the feeling. We need to remember that it always remains in us, even after the elimination of all acquired, external sensations. If I sit in a totally dark room, and stay perfectly still for some time while trying to disengage my phantasy from every image I have ever received, I will eventually arrive at a point where I seem to have lost all knowledge of the limits of my body. My hands and feet, and other parts of my body, will no longer be located in any discernible place. When I carry out this experiment as perfectly as possible, or try to arrive by abstraction at a moment anterior to all acquired sensations, I maintain that I still have a vital feeling of the whole of my body. It is easy to see, therefore, that if this feeling exists it must be very difficult to recognise and indicate because we do not normally pay attention to what is in us unless we experience change, without which we lack awareness, reflection and a means of comparison. Change is necessary for awareness; it is not necessary in order to have feeling.

Let us imagine that we move from a cold to an oppressively warm room. Obviously we notice the higher temperature immediately. But this is not the case with people who are accustomed to such warmth. For them it is tolerable and perhaps natural. Because they are used to it and experience it stably, they feel the warmth of the room without adverting to it. Hence, if we are going to believe we feel something, it must be enough simply to know that it acts upon our senses. We have to reason in this way: because the heat acts upon my senses, it is felt, although it may not be adverted to.

712. It may be objected that the feeling of life, or of being alive, which only death can obliterate, extends to all the sensitive parts of my body. In that case, it would seem that my feeling necessarily puts me in touch with the size and shape of my body without the intervention of sight and the other senses.
The objection is based upon a misunderstanding of the point at issue. The size and shape of our body are not comprised in the vital feeling of which we are speaking. This feeling alone would never enable us to form visible or tactile images of our body which depend upon the use of sight and touch. The phantasy simply imitates what our eyes and hands have presented to us. But the primal feeling contains nothing like this. What we see and what we touch is not the matter of this fundamental feeling. Indeed, we have already noted the difference between perceiving bodies through the (supposed) representations coming from our external senses, and perceiving our own body through the fundamental feeling. The two, or rather three kinds of perception of our own body, are to be kept separate and distinct (cf. 701-707). I cannot say: 'Perceiving my body in the first way (with the fundamental feeling), I do not perceive it in the third way (through sense-representations); therefore I do not perceive it at all.' This kind of argument is mistaken because it implies that the first kind of perception has to possess the characteristics of the third.

The real difficulty consists in forming a precise, clear-cut concept of the fundamental feeling. If more is demanded of the fundamental feeling than it actually possesses, it immediately appears absurd and pointless. But its denial in these circumstances is nevertheless unreasonable.

713. There is another difficulty to overcome. Attention is normally given to sensible representation of bodies, the third kind of perception which naturally holds our attention for several reasons. First, because exterior sensations are more vivid and impressionable than the other two kinds of bodily perception. Second, because sensations continually change and, as we have said, change draws the attention to differences and comparisons in such a way that we think we understand things only through this attention. Third, the direct act of understanding, through which our intelligence perceives exterior bodies, is our first, easiest and most natural intellection. On the other hand, in order to perceive intellectually our subjective body, we have to turn back and reflect upon ourselves. This is not easy. Drawn outside ourselves almost naturally, reflection is our last act and seems to lack light when compared with our vision of exterior things.(126)

714. Our primal feeling, therefore, does not make us know the shape or the visible size of our body; it makes us perceive our body in a totally different way, which can be grasped only by intense concentration upon ourselves and the vital feeling quickening us. As we turn our attention and observation to this feeling, we must be careful to become aware of it as it is, without speculating about its nature or adding to it products of our imagination and reason.

715. This feeling must also extend to all the sensitive parts of our body. To recognise this, it is sufficient to note the movements continually occurring inside the body, such as the circulation of the blood, the constant movement of liquid substances, the various kinds of assimilation, and the general vegetable life, which inevitably act on the sensitive parts of the body through the pressure they exercise. These facts also help to remove vestiges of doubt about the existence of the great number of small, habitual, unadverted sensations which take place in us unceasingly. It is clear that when a nerve is touched and modified some sensation must be present, even though our capacity for adverting to it distinctly has been obliterated by its constant recurrence.
I have no wish to investigate here the mysteries of the origin and continuity of life, but I must note that our habitual, fundamental sensation would be easier to understand if some interior movement amongst the components of the body were considered essential to life (and certainly here on earth such movement is a necessary condition for life). It is not difficult to conceive the existence of sensation where the sensitive parts of the body undergo change.

716. Some detailed observations may help us to understand that we feel our body continually.

1. We are unaware of the constant atmospheric pressure on all the parts of our body, even the most sensitive parts, although granted the surface of the human body (13,500 cm².), this pressure (12,922 kg.) produces a worse effect than if we were encased in a leaden suit. Uneducated people, who may claim that such a weight must be felt, can scarcely be convinced of its existence. Nevertheless, we do unconsciously feel the pressure because it is equally diffused over the surface of our body and is continually and habitually present. It is, as it were, something of ourselves, of our own substance (fish are in the same situation relative to the pressure of the water around them and would, if they could speak, deny any sensation). However, were we to change the air about us, we would soon be aware of our feeling. For example, climbing a very high mountain(127) where the air is rarer and lighter can produce vomiting, nausea, dizziness; the loss of pressure on our blood vessels can produce bleeding because the blood pressure itself is no longer held in check.

2. The same observation is applicable to the circulation of the blood itself which, coursing through the veins in so many intricate channels and impelled by a marvellous force, will certainly produce some habitual sensation. Nevertheless, despite the obvious pressure on the sides of the veins, it seems that this movement is either not felt at all, or hardly felt. Then, suddenly perhaps, a change takes place: the blood flows more rapidly or more slowly than usual as a result of inflammation or fright. Then the heart beats more rapidly, while veins and pulse tremble - or we faint. It was not the case that we felt nothing before the change; rather, we were unable to pay attention to the sensation because there was nothing new to attract our attention.

3. Our body has a certain temperature which we feel because we feel heat. Nevertheless, we scarcely notice it unless some change takes place. Let us imagine that different degrees of temperature, from freezing to very hot, are applied successively to a part of our body. We feel them all, and we notice that we feel them. Amongst these changes in temperature is the degree of heat normally experienced by our body which, however, we normally do not notice. We do notice it, however, amongst other variations in temperature because we compare various feelings produced by the different temperatures. Nevertheless, the comparisons we make do not produce the sensations. Comparisons are possible because we feel each sensation independently of any other, and independently of any comparison, although the comparison is necessary if we are to advert to the sensations which, however, exist even when there is no comparison and no passage from one sensation to another. We have to say, therefore, that we feel habitually the natural temperature of our body, although we do not notice this habitual sensation.

4. All the particles forming our body are attracted to the earth by the force of gravity. There is continual action on every molecule of our body and although we do not advert to it, some sensation must result from it. This is more noticeable in overweight people, but it also causes tiredness when people walk a lot. Nevertheless, we are naturally accustomed to a uniform feeling from the first moments of our existence, and normally are unaware of it. If, however, the attraction of gravity were to cease, or fall appreciably, we would experience a new kind of general sensation which would attract our attention by its novelty. We would notice in ourselves a sense of lightness, agility and mobility never before experienced. If the attraction increased suddenly, we would be overburdened by the weight of our body and immediately notice the change even in the shape of our body. On the other hand, without gravity our body would at least lengthen (there may be other difficulties as well) because all its particles, instead of pressing on one another, would tend to expand rather than move downwards. If these changes in the force of gravity caused a feeling in our body, this would take place because the attraction does indeed exercise an effect on our sensitive body and excite a feeling. This would also happen relative to the force actually exercised in normal circumstances, although the evenness of such a force would provide no stimulus for attention.

The same argument could be used about the cohesion present in the body, about the continual movements and alterations caused by breathing, digestion, growth and the infinite chemical changes taking place in us. Everything leads us to think that our body must be felt by us with a feeling of its own, made up of many tiny, particular feelings habitual in us from the first moments in which we are joined to our body.

But besides this complex of innumerable, particular feelings which fuse into a universal, constant feeling in the human being (as I have said, I do not wish to say whether they form part of life, although they are certainly necessary conditions for it in our present state), I believe that there is in the spirit itself, joined to matter and to being, a single, fundamental feeling that mingles with all other feelings, forming them into an undifferentiated, unknown something through which we feel our spirit with its body. It is a pure, very simple feeling, not an idea, from which it differs according to the distinction already established between ideas and feelings. According to this distinction feelings are the realisation of ideas.

717. Feeling, therefore, is an original datum. Consequently, we are not investigating its origin, but discussing its modifications and the genesis of sensations.

718. Those philosophers who imagine that human beings begin to exist without feeling truly make statues of them, and then go on to claim that sensations arise in these statues when they are touched by external bodies. Such a sequence of events, however, only creates inexplicable difficulties at odds with nature's normal way of acting. That feeling should suddenly arise where no feeling had previously existed would be as difficult to understand as creation from nothing. According to this hypothesis, sensation, which comes about in the statue when exterior bodies act upon it, informs us of our own existence. In this case, we feel something different from ourselves without being able to feel ourselves!

But the hypothesis (and it is nothing more than an hypothesis) is also contrary to the constant order of nature, which never works by leaps. There certainly would be a leap if we passed, when touched by an external body, from not feeling ourselves to feeling both ourselves and something outside. The external movement, which has nothing in common with sensation, would be accompanied by the creation of a spirit within us. How could we form the idea of a spirit totally devoid of any feeling and thought? Spirit has no extension, nor any other bodily qualities. Deprived of spiritual qualities such as feeling and understanding it is annihilated, or rather its idea is abolished from the mind even though imagination may pretend to fill its place with a spirit not attested by observation and consciousness.

719. All these reflections confirm the existence within us of a fundamental feeling. Serious attention to the nature of myself would indicate the existence of this feeling because myself, reflecting upon itself, in the last analysis discovers itself to be a feeling constituting the sentient and intelligent subject.

720. What we have said explains the classical teaching, repeated by St. Thomas, that 'the soul is in the body by containing it rather than by being contained'.(128)
The word 'body' indicates something known, as we noted earlier; we give names only to what we know (cf. 678). In order to know the meaning of body, therefore, we have to rely on experience (cf. 672-673), not on speculative reasoning or a priori deduction. Experience indicates as fact a certain action done in us of which we are not the cause. The essence of body was found consequently to be a certain(129) force modifying us (cf. 676). We feel this force from the first moments of our existence, although we do not advert to it; we feel it (cf. 715-716) in a constant, uniform way in a determinate mode; and this is what we call 'our body'. This force, although essentially different from myself (cf. 668-669), nevertheless acts in myself, in our spirit. We can rightly say, therefore, 'Our body is in our spirit' rather than 'Our spirit is in our body'. Later, we shall explain why common usage prefers the second to the first way of speaking.

721. This also explains why long arguments about the question of harmony between soul and body are unnecessary. We have to find the answer to this celebrated question in the fact provided by consciousness. Examining this fact, I find that which is passive to action and that which acts, that is, spirit and body. My body, therefore, is in fact and by definition a substance acting in a special way in my spirit. The physical influence needs no proof because it is already contained in the notion of body.

(112) Nevertheless what we shall say will throw light on the question.

(113) Any new condition changing the results would be reduced to a body's approaching or distancing itself, which is excluded by the formula. It is understood that no account is taken of the action of spirits; bodies alone are considered in their mutual relationships.

(114) If we were told about it, we would either have already experienced it with our senses, or not. In the first case, we would have some positive knowledge of the fact, together with belief in what we have been told; in the second case, we would only believe in such a change, our knowledge of which would be merely negative.

(115) My knowledge of corporeal capacities or forces, derived from their activity upon me, is the first knowledge I can possess about them. This must not be taken to imply that I cannot deduce other truths about bodies from my first knowledge. I simply affirm that my first experimental knowledge is the basis of all my other reasoning about corporeal qualities.

(116) This does not remove from sensation the extrasubjectivity I have spoken about, and which I intend to explain more fully later in this work.

(117) That is, animal life.

(118) Proofs of these assertions will be given later.

(119) We all know that our bodies are composed of sensitive and insensitive parts. The sensitive parts, we say, are the nerves. Albert Haller's experiments on the sensitive and insensitive parts are well known and have been repeated and confirmed in Italy by Leopoldo Caldani. These gentlemen had the patience and courage to experiment with a great number of dogs and other animals to test every part of the body and discover which parts were endowed with feeling and which not. It was love of humanity that made them cause pain to so many sentient beings. Later, other scientists introduced the expressions, 'vital contractility', 'vital force', etc., and claimed that in addition to life a certain latent sensitivity was present in all parts of the body. But Michele Araldi, speaking about Haller's distinction between the sensitive parts, says: 'Anyone who is not firmly convinced of this distinction and instead listens to futile systems is inevitably plunged into darkness where a single step irreparably ensnares him in errors.' Cf. Saggio di un' errata di cui sembrano bisognosi alcuni libri elementari delle naturali scienze, etc., Milan, Royal Typographer, 1812, p. 53.I cannot discuss this question now. It is sufficient that the nerves, but not other parts, definitely demonstrate signs of sensitivity when appropriately stimulated.

(120) We do not want to describe the union here, but simply indicate it under its own name to avoid confusion with any other kind of union.

(121) Some physiologists have pointed to apparent anomalies in this law. For our purposes, it is sufficient that sensitive and non-sensitive parts are present in the human body, given certain circumstances and moments.

(122) The change in our sensitive organ is still not feeling. Nevertheless, given that change, we feel because of our habitual feeling of the organ, whatever its state. Hence its changes are also felt. But we must not confuse: 1. the physical impression on the organ, with 2. our first feeling of the same impression.

(123) For example, communication with the brain. Without this, the organ feels nothing.

(124) Galluppi also describes this fact: 'I say that the spirit is intimately united and present to the whole body' (Saggio filos. sulla critica della conoscenza, etc., bk. 2, c. 6, §112). He adds that the mode of this union is incomprehensible. Relative to Galluppi's statement, note that exact knowledge of the fact equates to a sufficient knowledge of the union itself, as we shall see when I explain the fact, that is, when I explain its origin, which is all that is needed.

(125) I say a certain energy, not any kind of energy, because this energy has its own characteristics, as I have already noted. These determine and specify it, and I will deal with them later.

(126) The chronological order of feelings, therefore, is the inverse of the order of advertence to them. First, we have our interior and fundamental feeling; second, our exterior sensations. But we advert to our exterior sensations first, and then to our feeling. Moreover, in order to advert to our feeling, we need to have acquired control over our will, because we are free to reflect on and advert to our internal feeling. I have already shown, however, that we acquire this control over our thoughts only after having formulated abstract ideas (cf. 525-526). In order to advert to our interior feeling, therefore, we must have: 1. adverted with our understanding to our external sensations, and perceived bodies; 2. obtained ideas from these perceptions; 3. obtained (generic) abstract concepts from these ideas. When our spirit has developed to these three levels, and by means of the last of them, acquired dominion over our thought (which is done only with the help of language) (cf. 521-522), we are in a position finally to direct our thought to our interior, fundamental feeling. We see therefore that chronologically this thought is last and must be preceded by all the mental work on external sensations [App., no. 26].

(127) A rise of one degree in a barometer means a reduction of 61 kg. of atmospheric pressure.

(128) S.T., I, q. 52, art. 1.

(129) Later, when we perfect the definition of body, we shall specify the precise meaning of 'certain'.