Appendix 23. - (290)

This argument of Leibniz seems wrong to me. It is not, in fact, absurd to suppose that our organs, in order to produce a sensation in us, must be touched with a certain degree of force. If this degree of force is absent, the sensation does not occur; it begins only when the external impression has reached the degree of force required to produce a sensation in the organ. The impact upon the bodily organ and the corresponding sensation or perception which occurs in the soul must not be confused. That any external force, however small, acting upon our bodily senses, should produce some physical impression on them seems patently obvious. The phrase, 'external force', refers to something which is acting, to a small or great extent (according to its strength or weakness). Consequently, when what acts is applied to that on which it is called to act, it will undoubtedly produce some effects.

But are we obliged to believe that there is always some sensation in the soul corresponding to this slight action exerted upon the external sense organs? I have no doubt that every wave moved by the sea, moves the air slightly and that the air moved by the wave has an impact upon my ears. I go further: I am willing to believe that not only each wave, but each drop making up the wave moves the air proportionately to its own movement, and that the tiny wave movement is transmitted throughout the whole body of the atmospheric air. It affects not only my ears but the ears of persons further afield, decreasing as it goes. But it does not follow from this that the impact on my ear will be sensible for me, nor a perception for my soul. Experience shows that the impression of external things on the sensible parts of our body in the extremities of the tiny nerve ends should come from outside. It is important that the tremor or impact, however slight, should be transmitted to the brain. Once the link between nerve and brain is severed, sensations do not occur. Nor will every tiny impulse affecting the external nerves be sufficient to produce the amount of movement needed over the whole length of the nerve to arouse a sensation. It could be, that the impression of the external sensories has to have a certain degree of force merely to enable it to be transmitted and directed to the brain.

However, ignoring this, how did Leibniz acquire this view of his which I have refuted? Its source is an application of the law of continuity, to which he resorted a great deal. It is not my intention, at this point, to investigate this law or to assign its limits. The following observation should suffice to show clearly the wrong use the great philosopher made of it. What connection is there, I wonder, between the impression produced in the bodily organs and the corresponding perception in the soul? According to Leibniz's theory, these things are, by nature, totally different; one cannot be the cause of the other. One is certainly subsequent to the other, but it is a question of coexistence, not of cause and effect. Why, then, should I have to perceive every slightest impression formed in my external organs? Not by the law of continuity, because there is no scale of degree between the impression and the perception. They are things which are, by nature, different, arising as they do from completely different sources. Even if the law of continuity were to apply in this instance, it would apply only relative to the series of impressions on the one hand, and to the series of perceptions on the other. In other words, the same law would have to establish that a strong impression is impossible except through a series of prior, weaker impressions. Similarly, a strong perception would be impossible unless it were preceded by all the minor degrees of the same perception leading up to the strong force perception.

The law of continuity, therefore, will at most be applied separately to the series of impressions made upon the bodily organs on the one hand, and on the other to the series of perceptions of the soul. It can never be applied to the transition from one of these two series to the other because they are completely different in nature. Consequently, it is not at all absurd to suppose that the series of perceptions begins when the series of the degrees of impression is already well under way. In other words, perception does not arise in our spirit until our organs are moved by a certain degree of force. This is a law of nature which cannot be conjectured or deduced a priori but discovered only through experience. And constant experience convinces me that for every tiny impact which external things produce upon my bodily organs, there is certainly no corresponding perception in my spirit: perception only occurs when the impulse has a certain power. It may be, of course, that the degree of force required is more or less dependent on the difference in sensitivity of the organs with which different persons are endowed. I am willing also to admit that perception may be present without our being aware of it. In fact, we are continually having perceptions of which we are unaware because our attention is focused on other things and distracted by them. Nevertheless, it is essential that I should be aware of them when I turn my attention to them. If not, I would have to say that they are not present within me. I could not even say that they existed. Thus, however much I intend to smell the perfume of a flower, if I do not smell it I can only say either that the flower has no perfume or, if it has, that I have a cold in the nose or cannot smell anything. In other words, although my organ is always able to receive an external impression, it is not always able to receive it in such a way that there is a corresponding perception of the scent in my spirit. This can be said with at least a high degree of probability because I could on occasion be unable to focus my attention upon the perception. Experience shows that I have to acquire the ability to focus my attention on observing something occurring within me.

But this ability to focus our attention upon ourselves and direct it where we wish varies a great deal from person to person. Not everyone knows how to observe human nature, and only a few are alert and ready enough to reflect upon everything which occurs fleetingly and occasionally within them. The majority cannot do so. This explains the difference between philosophers and the masses, and between different philosophers. Again, one of the truly important circumstances which make it difficult for ordinary persons to focus their willed attention upon what happens to them individually is the minuteness and tenuous nature of the sensation. Highly vivid sensations draw our attention to themselves - violently, one might say - and tear it away from less vivid and strong sensations. On the other hand, if we wish to focus specifically upon them, we have to employ increased, inner, spontaneous vigour to counteract their own lack of power to stimulate and attract us. Because of this, it is indeed difficult to observe the minutest sensations within us. When we do observe them, we do so more easily if we dissociate ourselves from all other powerful impressions and we withdraw to somewhere dark and quiet where we can concentrate on ourselves. It is impossible, therefore, to assert categorically at this very moment that we do not have, for example, slight sensations of the very distant sounds of which neither we nor those around us can be aware however much we apply ourselves to listening for them. I conclude: the whole purpose of this long note is to bring out the difference between 1. unreflected sensations and 2. minute sensations. Leibniz confuses them, speaking now of one and now of the other as though they were the same thing. They, must however, be distinguished very carefully. From this distinction flows important consequences in the history of the human spirit. But I cannot deal with them here without straying too far from my original intent.

The reason we are not aware of our sensations, whether great or small, is that we do not reflect upon them, we do not focus our attention upon them, we do not think about them. Unreflected perceptions, therefore, are all those of which we are not aware. We do not know that we are having them. If asked whether we are having them, we are inclined to say no. Nevertheless we do have them.

The smallness of sensations is simply one of the many circumstances which very often deter us from reflecting upon them. We can indeed be aware of small sensations although this occurs in different persons according to their ability to reflect upon themselves and observe what is going on within them. Small sensations are not always or necessarily unreflected, that is, sensations of which we are unaware and cannot speak. Nevertheless, very frequently, they lie within us unobserved, unreflected. For this reason small sensations may be confused, as the great Leibniz confused them, with unreflected sensations. Again, we sometimes find highly vivid, powerful sensations which remain unreflected while all our attention is focused on a more interesting and powerful object. This explains why Archimedes, absorbed in solving a scientific problem dear to his heart, was unaware of the din created by the Roman army when it entered Syracuse.