Sensations [1] are impressions aroused in us when we encounter external objects. Modern philosophers have entirely abandoned the gross error that used to invest objects outside ourselves with the various sensations that we feel in meeting them. Every sensation is a perception that could not exist anywhere but in the mind, which is to say a substance that is conscious of itself and cannot be active or feel something without being immediately aware of it. Our philosophers go further than this. They make us note, with great clarity, that the sort of perception called 'sensation' is very different from, on the one side, what is called 'idea' and on the other from actions of the will and passions. Passions are, truly, confused perceptions which do not call up any object. But, as these perceptions end up in the selfsame inner self that produces them, the self does not return them anywhere but to itself, as affected in diverse ways such as joy, sadness, desire, hatred and love. By contrast, since sensations are felt by the self intrinsically, it relates them to the action of some external cause, and they usually bring with them the idea of some object. Sensations are also completely different from ideas.

1. Our ideas are clear. They distinctively evoke in us some object that is not us. By contrast, our sensations are obscure; they do not show us distinctly any object, although they attract our self as though to outside itself. For every time we feel some sensation, it seems to us as though some external cause is acting upon our self.
2. We control the attention that we pay to our ideas. We summon up this one, we dismiss that one; we call this one back, and hold on to it for as long as we wish. We pay it as much degree of attention as we please. We exercise control over all our ideas with an authority as complete as does a collector over the pictures in his study. That is not the case with our sensations. The attention we pay them is involuntary. We are compelled to pay it to them. Our inner self is involved in it, sometimes more, sometimes less, according to whether the sensation itself is weak or strong.
3. Pure ideas do not carry any sensation - not even those which represent corporeal objects. But sensations always have a certain link with the concept of bodies. They are inseparable from bodily objects, and it is generally agreed that they spring from some bodily movement, and particularly the one which external bodies pass on to our own body.
4. Our ideas are simple, or reducible to simple perceptions. For as there are clear perceptions which offer us distinctly some object that is not us, we can break them down until we arrive at the perception of a simple, unique object, which is like a point that we perceive in its complete entirety from a single glance. By contrast, our sensations are confused; and that is what leads us to conjecture that they are not simple perceptions, whatever the renowned John Locke  [2]might say. What helps our conjecture is the fact that every day we feel sensations that seem simple at that moment but which we later discover are not that in the least. It is known, from the ingenious experiments conducted with the prism by the renowned Sir Isaac Newton [3], that there are only five basic colours. However, from the various combinations of these five colours are formed that infinite diversity of colours which we admire in the works of Nature and those of painters, their imitators and their rivals, although their most ingenious paint-brushes can never be equal to it.

This blend of colours, tints, shades can be matched by just as many distinct sensations, that we might consider to be simple sensations like those of red and green, if Newton's experiments did not demonstrate that these complex perceptions are made up entirely from those of the five original colours. The same is true of the tones in music. When two or more tones of a certain kind come together to strike the ear at the same time, they produce a chord. A discriminating ear perceives these different tones at one and the same time without actually separating them, as they unite and melt into one another. It does not precisely hear any one of these two tones; it is a pleasant harmony that comes from them both, and out of them emerges a third sensation, which is called a 'chord' or a 'symphony'. Someone who might never have heard these tones separately would take the sensation born from their coming together to be a single perception. Yet it would not however have been any more so than the colour violet, which is the result of mixing red and blue on a smooth surface in equal small portions.

Every sensation — for instance that of tone, or of light in general, however simple, however indivisible it might appear to us, is a complex of ideas, a combination or mass of small perceptions which succeed each other in our inner self so swiftly , with each one enduring so very briefly, or which appear all together in such large numbers that the self, unable to distinguish one from another, has only a single, highly confused perception of that complex regarding the small parts or perceptions that make it up. But on the other hand, the perception will be very clear, to the extent that the self sets it distinctly apart from every other sequence or combination of perceptions. Hence it comes about that each confused perception, if looked at on its own, becomes very clear when you place it in opposition to a different sensation. If these perceptions did not follow each other so swiftly, or if they [4] did not appear all together in such large numbers, or if the order in which they occur and follow each other did not depend on the order of the external movements, or if the self had the power to change it — if all that could happen, sensations would be no more than pure ideas, representing various kinds of movement. The self pictures them well, but in miniature, and with a speed and wealth that cause it confusion, preventing it from sorting out one idea from another, even though it is forcibly struck by the whole ensemble together and distinguishes very clearly one particular sequence of movements from another sequence, one order, one mass of perceptions from another such order and mass.

Beyond this first question, considering whether sensations are ideas, one may pose several others, so rich does this topic become, as you look more and more closely into it.

1. The impressions borne in upon our inner selves by sentient objects— are these arbitrary? Clearly not, it seems, since there is an analogy between our sensations and the movements that produce them, and since these movements are not the simple conjuncture but the very object of these confused perceptions. This analogy will become clear, if on the one hand we make comparisons within these sensations, and if on the other we compare the organs producing these sensations and the impression that is made upon these different organs. Sight is something more delicate and more skillful than hearing; hearing has obviously a similar advantage over smell and taste; and these two last kinds of sensation similarly triumph over touch. These same differences can be perceived between our sensory organs for the make-up of these organs, the delicate quality of the nerves, the subtlety and speed of the movements, and the dimensions of the external bodies having an immediate effect upon these organs. The physical effect upon the sense organs is merely a touch, more or less subtle and delicate, when related to the nature of the organs that must be affected by it. The organ that provides vision is the lightest of them; noise and sound have a less delicate effect on us than light and colours, while smell and taste are yet less so than sound; but heat and cold and the other tactile qualities have the strongest and crudest effect. In every case, it requires only varying degrees of the same sort of movement to transport the soul from pleasure to pain. This is a proof that pleasure and pain, whatever is agreeable or disagreeable in our sensations, is perfectly analogous to the movements that produce them or, to express it better, that our sensations are only the confused perceptions of these diverse movements. Besides, when we make comparisons between our sensations, we discover likenesses and differences that show a perfect analogy with the movements that produce them and with the organs receiving these movements. For example, smell and taste are very close neighbours and show quite a lot of both. The observable analogy between senses and colours is much more evident. We must soon come on to these other questions and probe more and more deeply into the nature of sensations.

Why, one asks, does the soul relate its sensations to some external cause? Why are these sensations inseparable from the concept of certain objects? Why do they make such a strong impression upon us and oblige us to see these objects as existing outside of our selves? Furthermore, why do we regard these objects as not only the cause but as it were the subject matter of these sensations? Whence, finally, does it come about that sensation is so intermingled with the concept of the object itself, although the object is distinctly separate from our self, where sensation is not? It is extremely difficult, or even impossible, for our self to separate sensation from the concept of this object, as is mainly the case with vision. When you see a red circle, it is hardly any easier to prevent yourself from attributing the quality of redness (which is your own sensation) to it than attributing to it roundness (the very property of the circle itself). So many questions to clarify regarding the sensations; they show clearly enough how thorny the problem is. Here is more or less the most reasonable answer to it one can offer.

Sensations take the self outside itself by offering it the unclear notion of an external cause acting upon it, because sensations are involuntary perceptions. In so far as it feels something, it is passive, being the subject of an action. Therefore there is an agent outside it. What will this agent be doing? Reason suggests thinking of it as proportionate to its action and believing that different effects are the results of different causes, that sensations are created by causes as varied from one another as are the sensations themselves. Following this principle, the cause of light must be other than the cause of fire. What causes in me the sensation of yellow must not be the same as what gives me the sensation of violet.

Since our sensations are perceptions reflecting an infinite number of small indiscernible movements, they naturally bring with them the notion, clear or confused, of the body which cannot be separated from the notion of movement. Besides, we naturally regard matter as agitated by these diverse [5] movements, as the universal cause of our sensations, at the same time as its object.

By another consequence, which is just as natural, it happens that our sensations are the most convincing proof we possess that matter exists. Through them, God informs us of our existence. For although God is the universal and immediate cause acting upon our inner self about which, when we reflect on it, we clearly see that matter cannot have a real physical impact); although the sensations that we are feeling at every instant are enough to prove that there is outside us a spirit whose power is infinite, yet the reason why this omnipotent spirit subjects our self to this succession, so varied yet so well-ordered, of confused perceptions that possess nothing but movements as their object — this reason cannot be derived from elsewhere than these movements themselves, which occur effectively in matter that actually exists. The aim of the infinite spirit, which never acts by chance, cannot be other than to demonstrate to us the existence of this matter by these diverse movements.

There is no way more appropriate of teaching us this fact. The notion of matter, on its own, would reveal its nature to us, but would never teach us that it exists, since it is not essential that matter should exist. But the involuntary way that our self takes on this notion , embedded within the notion of an infinite number of successive modifications that are arbitrary and not essential to this notion, leads us infallibly to believe that it exists with all its diverse modifications. The self, led by the creator along this orderly succession of perceptions, is convinced that there must be a material world outside itself, which is the foundation, the exemplary cause of this order, and with which these perceptions have a basis of truth. Therefore, although amidst the huge variety of objects that the senses present to our mind, only God acts upon our mind, each sentient object with all its properties may be credited with being the cause of the sensation that we experience of it, because it is the sufficient cause of this perception and the basis of its truth.

If you ask me the reason for this, I shall reply that it is...

1. Because we feel, on countless occasions that while there are some sensations which inevitably find their way into our inner self, there are others over which we have free control, whether by recalling them or by dismissing them according as we wish. If I look up at the sun at noon, I cannot avoid receiving the ideas which the sunlight then evokes in me. Whereas if I close my eyes or find myself in a dark room, I can recall freely to mind the ideas of light or sunshine that prior sensations had placed in my memory. I can also abandon these ideas whenever I want, so as to concentrate on the smell of a rose or the taste of sugar. Clearly, this variety of ways in which our sensations present themselves automatically to our self suggests that some are awakened in us by the lively impression of external objects (which dominates us, informs us and guides us regardless); while others are evoked by the simple memory of the impressions that we have already felt.

Besides that, there is no one who does not intrinsically feel the difference between contemplating the sun, according to the notion one has of it in one's memory, and actually looking at it: two things so perceptibly distinct in the mind that few of its notions are more distinct from one another. So one clearly recognizes that neither is the effect of one's memory or of one's mind or of pure fantasies created within oneself, but that the sight of the sun is produced by a cause.

2. Because, clearly, those who are deprived of organs producing a particular sense can never contrive that the ideas relating to that sense be in fact produced in their minds. It is so manifestly a truth that it cannot be called into question. Consequently, we cannot doubt that these perceptions come into our minds by the organs of that sense and not by any other way. Visibly, the organs do not produce them. For, if that were so, one's eyes would produce colours in the dark, and one's nose would scent roses in winter. But we never see anyone acquiring the taste for pineapples before they have gone to the Indies where that excellent fruit is to be found, and actually tasted them.

3. Because the feelings of pleasure and pain affect us quite differently from the simple recollection of one or the other. Our sensations provide us with a clear knowledge of something more than a simple intimate perception; and this extra is a modification which, more than a particularly lively feeling, conveys to us the concept of a being that actually exists outside us, which we 'call 'body'. If pleasure or pain were not caused by external objects, the recurrence of the same ideas should always be accompanied by the same sensations. But that does not happen. We remember the pain caused by hunger, thirst and headache without feeling any discomfort from them. We think of the pleasures that we have enjoyed, without being invaded or filled by delicious feelings.

4. Because our senses, in several instances, send one another evidence of the truth of their links regarding the existence of sensory things that are exterior to us. Anyone who sees fire can also feel it. If they doubt that it is anything other than simple imagination, they can convince themselves by putting their own hand in the fire. For you certainly could never experience such an intense pain from a pure idea or simply an apparition, unless that pain is itself imaginary, which you could not however recall to mind by evoking the concept of burning after it has healed.

So, in writing this, I see that I can change the way the paper looks and can tell in advance by writing letters down, what new idea it will offer my mind in the following instant, by means of a few strokes that I shall make with my pen. But it will be useless for me to imagine those strokes if my hand does nothing or if I keep my eyes closed when I move my hand. Besides, once these letters are written down on the paper, I cannot avoid seeing them as they are, which is to say having ideas arising from those letters which I have formed. From that, it can clearly be seen that this is no caprice of my imagination , since I find that the characters which have been written down according to the play of my mind no longer depend on that caprice, and do not cease to exist the moment I imagine that they are no longer there. On the contrary, they continue to exert a constant and unremitting effect upon my senses, according to the shape that I have given them. If you also add that someone else seeing these characters will pronounce the same sounds I had intended them to have, it will be impossible to doubt that those words which I am writing really do exist outside of me, since they produce this long succession of regular sounds by which my ears are presently being struck, and that my memory can never retain in that order.

5. Because if bodies do not exist, I cannot imagine why, when hearing in what I call a 'waking' moment that someone is dead, it will never again occur to me that they are living, and that I can talk and dine with them during the whole of my time of wakefulness and have my wits about me. Nor do I understand why, having begun to think that I am on my travels, my state of aberration will conjure up new roads, new towns, new hosts, new houses, or why I shall never think to find myself in the place which I seem to have left. Nor do I know any better how it can be that while I believe I am reading an epic poem, or tragedies and comedies, I can pen excellent verses and produce an endless array of fine thoughts, when my mind is so sterile and so crude at all other times. But the most astonishing thing is that it is for me to recall all these miracles whenever I choose. Whether my mind is willing or not, it will not think less well, so long as it imagines that it is reading a book. This imaginative capacity is its only resource, its only talent. This illusion allows me to read by turns Pascal, Bossuet, Fénelon , Corneille, Racine, Molière, etc., in a word all the greatest geniuses, whether ancient or modern, who must be for me no more than imaginary figures, assuming that I am the only person in the world and that bodies do not exist. Peace treaties, the wars to which they put an end, fire, fortifications, weapons, wounds,: all that, just a dream. All the care we take to improve our knowledge of metals, plants and the human body: all that will for us make progress only in the realm of ideas. No fibres, no juices, no fermentations, no seeds, no animals, no knives to dissect them, no microscope to study them; but instead of a notional microscope, my mind will give birth to ideas of wonderful arrangements in small, ideal portions.

I do not deny, however, that there may be men who in their sombre meditations have so far weakened their minds by continual abstractions and, dare I say it, so befuddled their brains with metaphysical possibilities that they really doubt whether bodies do exist. All one can say about these contemplatives is that they have lost the common touch, thereby misunderstanding a prime truth ordained by the feeling of Nature, which finds its justification in the unanimous agreement of all human beings.

It is true that one can raise difficulties about the existence of matter. But these difficulties serve only to show the limits of the human mind, along with the feebleness of our imagination. How much does someone propose arguments that confound our own, and which nonetheless do not, and must not, make any impression on commonsense? Because these are illusions, whose falsity we can well perceive through an impeccable natural feeling, though we are not always able to prove it by a precise analysis of our thoughts. Nothing is more ridiculous than the foolish confidence of certain intellects, who exploit our inability to reply to answer objections, where we must be convinced, if we are sensible that we can understand nothing.

Is it not most surprising that our minds go astray in the concept of infinity? A man → like Bayle [6] would have demonstrated to anyone willing to listen that it was impossible to see corporeal objects. But his problems would not have destroyed the daylight, and we would no less have made use of the spectacle of Nature, for dialectic arguments must give way to the reality of light. The two or three walks taken by the Cynic Diogenes [7] in public perform a better job at refuting the foolish sophistries contesting the existence of movement than every kind of reasoning.

It is rather a comic spectacle to see philosophers exerting every possible effort to deny the action conveyed or consistently impressed on them by the sight of Nature, and then doubting the existence of the lines and angles that is their basis every single day.

Once you admit the existence of bodies as being a natural consequence of our diverse sensations, you can see why, very far from any sensation being solitary and divorced from every concept, we have so much trouble in making a distinction between the concept and the sensory awareness of an object. Up to that point, by a kind of contradiction, we endow the object itself with the perception that gives rise to it, by calling the sun luminous , and looking at the striking colours of a flower-bed as something that is inherent in the border rather than in our inner self, even though we do not imagine that the flowers of this bed perceive things in the way we do. Herein lies the mystery. Colour is no more than a way of perceiving flowers; it is a modified form of the concept that we have of it, in so far as this concept belongs to our inner self. The concept which I have of a circle is not that circle, since that circle is not a basic aspect of my self. If therefore the colour in which I see that circle is also a perception or basic aspect of my self, the colour belongs to my self, in so far as it perceives that circle, and not to the circle as it is perceived. From where then does it come that I ascribe redness to the circle just as much as roundness? Would there not be something in a circle, by virtue of which I see it only as a sensation of colour, and of red colour rather than violet colour? Probably, yes; and this is a certain modified form of movement imprinted on my eye, upon which that circle has the power to project, because its surface transmits to my eye only the gleams needed to project shocks, the confused perception of which is called red. Therefore I possess at one and the same time the concept and the sensory impression of the circle.

Through clear and distinct thinking, I see the circle as round and extended., and so I ascribe to it what I can see clearly: extent and roundness. Through my senses I perceive, in some confusion, a multitudinous succession of indiscernibly small movements, which evoke in me he clear concept of the circle, but show it to me as acting upon me in a particular way. All that is true. But herein lies the error. In the clear concept of the circle I can distinguish the circle from the perception which I have of it; but in the confused perception of the small movements of the optic nerve, caused by the light rays reflected by the circle, since I do not see any distinct object, I cannot easily separate this object, that is to say this rapid succession of small shocks, from the perception which I have of it. I immediately confuse my perception with the object perceived; and since this confused object (that is to say, this succession of small movements) relates to the object itself, which I rightly assume to be outside of me as being the cause of these small movements, I also attach the confused perception which I have of it to the object itself; and I endow it, so to speak, with the sense of colour that I have in my inner self, by considering this sense of colour as being a property, not of my self, but of this object. Thus, instead of saying that the red is in me a way of perceiving this circle, I say that the red is an aspect of the perceived circle. Colours form an outer coat with which we cover material objects; and as bodies provide the basis for those small movements which show us that they exist we consider those same bodies as being the basis for the confused perception that we have of these movements, being unable to distinguish between objet and perception, as invariably occurs with confused perceptions.

This observation which we have just made regarding our errors in judging confused perceptions may help us to understand why the self, possessing such a sense of its own body, is mixed up indiscriminately with it, attributing to it what are its own sensory reactions .It is that, on the one hand it has a clear notion of its own body and distinguishes it clearly from itself. But on the other hand it has a mass of indistinct perceptions relating to the overall order of movements occurring in every part of this body. Hence it comes about that it attributes to the body, of which in general it has a clear notion, these same confused perceptions, believing that the body is aware of itself, whereas it is the inner self which is aware of the body. Thus it imagines that it is the ear which hears, the eye which sees, the finger which suffers pain from a bite, whilst it is the self, being attentive to the movements of the body, which does all that.

As for external objects, the soul has with them only an indirect link, which more or less preserves it from error, but does not save it completely. It discerns them as separate from itself, because it looks upon them as the causes of the various changes occurring to it. Yet it still confuses the two in some respects by attributing to them its sensations of colour, sound, heat as their properties inherent in them, for the same reason that made it confuse itself with its own body, when it says quite naively:' 'it is my eye that sees colours, it is my ear that hears sounds', etc.

But whence does it come about that amongst our various sensations, we attribute some to external objects and others to ourselves, and that we lack any firm viewpoint so far as some of them are concerned, since we do not really know what view to take of them, since we can judge of them only through our senses? Malebranche [8] specifies three kinds of sensations: (a) some strong and lively, (b) others weak and inert, and finally (c), those which are between both those two categories. Strong and lively sensations are those which astonish the mind and shake it with some degree of forcefulness, because it finds them very welcome or very unwelcome. Now, the self cannot fail to recognise that such sensations are its own to some degree or other. So it concludes that heat and cold do not exist exclusively within ice and fire but that they are also inherent within itself. As for weak sensations, which have very little effect upon the self, we do not believe that they belong to us nor that they exist within our own body, but solely in the objects with which we endow them. The reason why we do not perceive at once that colours, odours, tastes and all the other sensations are modifications of our self is that we do not have any clear concept of this self. This ignorance means that we do not know by a simple perception, but only by reasoning, whether light, colours, smells, tastes and all the other sensations are or are not modifications of our self. But as for lively sensations, we can easily judge that they are within us, because we clearly feel that they touch us and that we do not need to know them intellectually in order to know that they belong to us. As for intermediate sensations that have a moderate impact on our self, like a strong light or a loud sound, the self finds itself much perplexed.

If you ask Father Malebranche why the Creator has devised this arrangement, he will reply that since such strong sensations are capable of doing harm to our limbs, it is right and proper that we are given a warning when these limbs are under attack, so as to prevent their being damaged. But the same thing does not apply to colours, which cannot usually harm the retina where they collect together, so it is not necessary for us to know that they are represented there. These colours are needed by us only for us to have a clearer knowledge of objects, and that is why our senses lead us to attribute them simply to objects. Thus, concludes Malebranche, the judgments to which our senses lead us are very sound, if we consider them in relation to bodily self-preservation; but they are most fanciful and very far removed from the truth if we are looking at them with respect to what bodies are in themselves.

Notes

1. While I have tried to keep to the French text as closely as possible, it seems to me that to render 'l'âme' as 'soul' is to give it a theological character that would be out of keeping with the secular approach that the Encyclopédie generally represents I have variously translated it as '(inner) self'.

2. John Locke (1632-1704), author of An Essay concerning Human Understanding (1689). Presumably, the author has in mind statesments such as that 'the great source of most of the ideas we have, depending wholl upon our senses [...] I call SENSATION' (II 1.3). This touches on the distinction commonly made (often rather simplistically) between Lockean empiricism and Cartesian rationalism. The Author may well be influenced by Malebranche, who views sensations as purely subjective and fundamentally distinct from 'ideas'. One commentator sums up quite pithily Locke's position on sense-perception: 'The obtrusiveness of sensation is what makes it a kind of knowledge for Locke' (P.Sheridan. Locke , London / New York, 2010, p.104).

3. Isaac Newton (1642-1726), author of Optics (1704). This work had become very popular from the 1720s, going through several editions in French and Latin.

4. The text erroneously has 'elle'.

5. The text gives 'divins (divine)', which is surely an error. The word does not appear anywhere else in this article, and seems to have no relevance to the argument. It is true that the article goes on to discuss the existence of God, which lends some ambiguity to the matter. But that would not seem to be a relevant consideration here.

6. Pierre Bayle (1647-1706), author of the Dictionnaire historique et critique (1696; English translation , 1710), was commonly seen as a sceptic (if not occasionally a downright atheist) in the 18th century. Elisabeth Labrousse, a leading scholar on Bayle,, shows that while broadly true, such a description does not fairly represent the complexity of his philosophy. ( Bayle , OUP, 1983, p.74).

7. Diogenes of Sinope (generally known as Diogenes the Cynic) (c.412 BCE - c.323 BCE), founder of the Greek School of Cynicism.For him, civilisation was a sham. He lived an extremely ascetic existence, reputedly going about dressed clad in only a clay pot. He was often seen in the eighteenth century as the prototype of the totally honest ← man; for example, Diderot, Le Neveu de Rameau , ed J. Fabre, Droz, 1963, p.106.

8. Malebranche, Nicolas (1638-1715), author of De la recherche de la vérité (1675-76), (III..iv).