Science ceases to exist where necessary connection loses its forceF. Engels, Dialectics of Nature

Painting is born of sight. Sight is one of the acts by which a human being perceives the impacts of the external world. Painting is a product of human activity. If that activity is born of visual perception, then to bring out the foundations of painting one must study the connection between them, that is, the character of the dependence between painting and visual perceptions.

To study this dependence one must examine in detail, on the one hand, the visual process, which is of extreme complexity, and on the other, what elements painting consists of and by what means it is made.

Having established which moments in the process of visual perception carry a definite significance, both in the making of paintings and in the visual perception of painting itself, and setting these against the means of expression that painting possesses, one can determine the dependence between the facts of a person's visual perception of the external three-dimensional world and the various means of expression that painting has at its disposal.

Since the facts of this dependence, once established, are the same whether we are perceiving paintings or making them, these facts make it possible not only to classify paintings, but also, on the basis of the presence in them of one element or another, to judge the characteristic features, or “types”, of those works.

Before taking up visual perceptions and their relation to painting, we should dwell briefly on perception in general, and then on what the concept of painting covers.

Perception. Every consciousness marks itself off from the external world (I and not-I). The impacts of the external world are perceived by our consciousness through the sense organs (receptors). The act by which a person perceives an impact of the external world consists, in broad terms, of three components, studied separately by physics, physiology and psychology. A physical agent excites a physiological process, and parallel to that process psychic experience runs its course.

Within this psychic experience of “perception”, psychology distinguishes:¹ 1. sensation, and 2. the thought that is born with that sensation and is inseparably bound to it. Distinguishing the sensation itself from the thought that accompanies it matters greatly, because each of these parts of perception has its own distinct properties and, moreover, the weight of each may vary in inverse proportion to the weight of the other. If the attention of consciousness is turned to one part, the other pales: strong sensation drives out thought, intense thinking washes sensation away. Thinking itself may be regarded as a reflex upon sensation.²

In distinguishing “sensation” from “thinking” within perception, one cannot fail to notice that sensation, as the experiencing of an impact of the external world, is a passive experience, whereas “thinking” within perception is already an activity of consciousness, that is, already “work”.

Psychology holds that a sensation cannot be transmitted from one consciousness to another, but is only experienced by each consciousness in its own way. I can have no notion of how another experiences the sensation I call the colour red; a thought, on the other hand, passes from one consciousness to another in words: if I say “right triangle” or “square”, I convey to another an entirely exact concept of a geometrical figure.

It is of the highest importance that sensations determine the attitude of consciousness to the perception itself, whether that attitude is positive or negative (whether it pleases or does not please), and this appraisal is subjective in the sense that it is available only to the given consciousness. Toward “thought”, consciousness takes the view of its correctness or incorrectness in the sense of its accessibility to another consciousness, and appraises it, even if subjectively, from an objective standpoint (logic).

Painting. Concerning the concept of “painting” the following preliminary considerations must be set out. To begin with, the word “painting” denotes both the act of making a painted work and its result, that is, the painted work itself. By the latter one may understand everything a person depicts by means of a colouring substance on a surface. But what interests us is not painting of any kind whatever, but painting that “depicts” the three-dimensional forms of the external world, and not symbols, that is, letters, signs, ornament and the like. Whatever painting may depict, it can only depict forms of the external world, since even when it sets out to create forms that do not exist in nature, it can only create combinations of forms taken in by sight from the external world.

Painting that wishes to depict something not drawn from visual perceptions received earlier can give not forms but only symbols: letters, figures, signs, which when perceived act wholly upon thinking and only minimally upon sensation. Visual perception, as has been said, is the action of the external world upon consciousness, and painting, in the sense of the painted work, being an object of the external world, is itself an object of visual perception. From this it follows that visual perceptions give consciousness representations of the forms of the external world, and painting likewise gives representations of the forms of the external world, but the means and conditions by which representations of the forms of the external world are formed through sight, and the means and conditions by which they are formed through painting, are very different. What is that difference in means and conditions? The chief difference is that through visual perception we receive representations of the forms of the three-dimensional external world from those forms directly, whereas painting, in order to call forth a representation of three-dimensional forms, offers our sight the surface of a picture or a drawing, that is, it seeks to call forth a representation of the forms of the three-dimensional world from colouring material laid on a two-dimensional plane. In other words, in nature all three dimensions of every form are taken in by sight; in painting on a plane only two of them can be given directly, and the third must somehow be suggested.

Moreover, when we look at the three-dimensional external world we see it by means of the light reflected into our eyes from its three-dimensional forms, and also from the sources of light themselves, if any are within the field of view.

In painting, its whole small two-dimensional surface reflects into our eyes the light falling upon it, in the gradations regulated by the paint; sources of light, that is, independently luminous, light-emitting parts, do not exist in a painting.

From this it is clear how much poorer the visual perception of forms depicted by painting must be than the visual perception of the forms of the three-dimensional world itself.

Yet painters in every age have tried, and still try, to make their painting as rich in means as possible, so as to bring the impressions it gives closer to the impressions received from forms perceived from nature. Many have achieved this, and still achieve it, by their own routes; a still greater number try to make use of the experience of others. The whole pedagogy of painting bears witness to this.

Finally many, having grasped the impossibility of giving the three-dimensional world in full in two-dimensional painting, and the difficulty of approaching it, consciously renounce such an approach and work out various means of expression in their painting, cultivating them with greater or lesser success.

If one surveys all the painting recorded in the history of art, and its authors, it is not hard to notice that all those artists who never abandoned the task of giving in painting representations of forms as close as possible to the representations received visually from nature, and who succeeded in it, have all been valued and are still valued as the finest representatives of the art of painting. The same estimation has been won by those artists who, renouncing this “approach to nature”, independently cultivated their own conventional forms of expression, redeeming that renunciation by the depth and interest of the content of their works.

The study of the properties of the human eye has widened considerably of late, thanks to research in photometry within physics together with the study of the function of the eye by physiology and psychology. These advances in the study of the eye undoubtedly owe a debt to earlier work in optics. The technical improvement of optical instruments has made it possible to study the eye too as an optical instrument. The developed theory of improved optical instruments established the requirements that define the merits of such instruments. Clearly, in studying the eye as an optical instrument and comparing it with them, all the properties of the eye came to be qualified as positive or negative from the point of view of the requirements that define the merits of optical instruments. Thus, for example, the ability of the eye to change the radius of curvature of the front surface of the lens is a positive quality and even an advantage over optical instruments, whereas the lack of achromatism in the normal eye, together with spherical aberration, is counted among its defects; the field of view of the eye is wider than that of optical instruments, and that is a positive quality, while the fact that only a small part of that field serves for clear vision is a defect. S. Maizel, in his work Light and Vision,³ says: “There are further defects, depending on the structure of the lens and so forth, so that all in all the eye is far from a faultless optical instrument. Yet all these defects belong to a perfectly normal eye, it grows accustomed to them, and one way or another they enter into its normal functioning. It is quite impossible to abolish them, and so they must be accepted as given, and in the further study of light sensations need not be specially reckoned with.”

So all these “defects” of the eye, on the assertion of science, “belong to a perfectly normal eye” and “it is quite impossible to abolish them”; consequently they are all “defects” only when the eye is compared with optical instruments, while at the same time they are the eye's own normal properties, and not defects at all.

Almost all people not only do not regard them as defects but, using their eyes all their lives, do not even suspect that these properties exist. To determine the relation between painting and sight, however, these properties require careful study, together with their influence on visual perception and then the way they tell upon painting.

The structure of the eye. Let us recall the familiar scheme of the optical structure of the eye by means of a drawing of its section by a vertical plane passed through the line joining the centre of the pupil and the centre of the retina. The shape of the eyeball is close to a sphere. The ball consists of an outer firm coat (sclera), which is opaque except for the part in front of the pupil, where the sclera passes into the transparent, spherically convex cornea. Transparent is the part covering the coloured iris with the pupil at its centre. The pupil is an opening in the iris, and it changes its diameter according to the quantity of light falling into the eye and the demands of accommodation.

Adjoining the iris on the inner side of the eye is the lens (crystallina, transparent). It has the form of a biconvex lentil and can change the radius of curvature of its front surface by the contraction of the muscles that hold it. This lens divides the inner volume of the eyeball into two unequal parts: the outer, between the cornea and the iris, filled with the aqueous humour, and the inner chamber, filled with the vitreous humour. The refractive index of the lens is greater than the indices of both fluids, and this makes the lens the objective of the optical system. As an objective, the lens casts on the back inner surface of the eye an image of the external world lying before it. This back inner spherical surface, of extremely complex structure, is called the retina and contains the light-sensitive elements of the eye. The description of these elements and their functions I take from S. Maizel's Light and Vision:³ “The optical system of the eye casts an image of the objects of the external world on the retina. The question is, what in the retina is subjected to light stimulation, and how is the stimulation thus received passed on to the brain? The second question is formally very simply answered: as in all organs, the transmission of stimulation to the brain centre proceeds along a nerve, in this case the optic nerve. It enters the eyeball, and the nerve fibres composing it, diverging in every possible direction and lining the floor of the eye with their plexus, form the base of the retinal coat. A cross-section of the retina reveals in it a complex structure of a series of layers. This section is shown in somewhat schematised form in the drawing.⁴ Passing from outside, light penetrates a series of retinal layers and reaches at last the final layer, which contains the light-sensitive elements. There are two types of these, called rods and cones. These rods and cones sit at the centres of hexagonal cells, which give the whole light-sensitive layer of the retina an appearance recalling a mosaic or a honeycomb. The number of these elements is very great: it is reckoned that over the whole retina the cones amount to 7 million and the rods to 130 million. Their distribution over the retina is very uneven: in the part adjoining the direction of the optical axis of the eye the cones predominate and the rods are very few; toward the periphery of the retina, on the contrary, the number of cones falls off rapidly and the rods alone remain. On the retina there is a particular place, lying not on the optical axis but somewhat to one side of it, nearer the temporal part of the head, called the yellow spot (macula lutea) on account of its colour. This part of the retina has at its middle a small central depression (fovea centralis), which plays an especially important part in the act of vision. Toward this depression the thickness of the retina within the yellow spot decreases, almost all its intermediate layers disappear, and practically only the rods and cones with their nerve endings remain. In the fovea itself the rods disappear too, so that its whole floor is lined with cones alone, whose number here reaches approximately 13,000 to 14,000.

It is upon this depression in the yellow spot that the eye involuntarily directs the image of the object it wishes to see clearly, performing what is called the fixation of vision. Any deviation of the image away from the fovea entails a loss of clarity of discrimination, and when the image leaves the yellow spot altogether, the discrimination of small details of the object ceases entirely.

The dimensions of both cones and rods are very small. The length of the cylindrical (so-called outer) part of the rods, made up of thin leaflets laid one upon another, is approximately 0.03 mm, and its diameter 0.002 mm. The height of the cone of a cone-cell is approximately 0.01 mm. The widened (inner) parts of rods and cones have a more or less identical, roughly ellipsoidal form, but in the cones they are somewhat larger than in the rods. Both rods and cones sit on fibres of greater or lesser length ending in branchings, only the fibres of the cones are considerably thicker than those of the rods. The branchings of the fibres lie against the finest branchings of the optic nerve. Under the influence of light the fibres of the cones contract strongly, and in darkness they lengthen again.

In the rods a particular pigment has been found, the “visual purple” (rhodopsin), which gathers in them in darkness and bleaches in light. Vision by the rods is undoubtedly conditioned by the chemical action of light on rhodopsin. In the cones no substance has so far been discovered on which light would act directly. Besides the visual purple, the floor of the eye possesses one further pigment, black in colour, whose role is to protect the light-sensitive apparatus from excessively strong light stimulation. In the absence of light stimulation the grains of this pigment sit on the rear surface of the retina (away from the cornea), practically outside it. But under the action of light the grains begin to move toward the incoming light, penetrating the layers of the retina and, absorbing a considerable part of the light energy, screening the rods and cones to a great degree from light stimulation.

The immediate mechanism by which light stimulates the rods and cones cannot at present be regarded as known. There are a good many hypotheses, more or less well founded, but none has won sufficiently wide acceptance. One thing is beyond doubt: in one way or another the processes arising in the rods and cones are passed through their inner parts to the fibres on which they sit and to their branchings, and from the latter to the finest fibres of the optic nerve. In the region of the fovea a separate fibre of the optic nerve runs to each cone. In the yellow spot separate fibres likewise run to most of the cones, but sometimes whole groups of them are served by a single fibre. Outside the limits of the yellow spot a single optic-nerve fibre always serves whole groups of cones or rods. Since the total number of rods and cones over the whole retina approaches 140 million, while the number of optic-nerve fibres is of the order of one million, on average about 150 light-sensitive elements fall to a single fibre. For this reason it is only in the region of the fovea and the yellow spot that the eye can discriminate fine detail; in the remaining parts of the retina whole groups of elements occupying a comparatively large area pass their stimulation simultaneously to one nerve fibre, and the picture received by consciousness becomes coarse and devoid of detail.

The total field of view of the eye is enormous, greater than that of any other optical instrument whatever, but in reality only an insignificant part of that field can be used for the purposes of clear discrimination: of the order of 1 to 1.5 degrees vertically and horizontally for foveal, the most perfect, vision, and about 8 degrees horizontally and 6 degrees vertically if vision over the whole yellow spot is counted as sufficiently satisfactory. All the remaining part of the field of view serves only for rough orientation, and not for vision in the true sense of the word. In consequence of this feature of the light-sensitive apparatus, the eye is obliged to perform a continuous rotary movement within its orbit in order to survey the surrounding space. This rotation brings the images of ever new places in the external world onto the fovea and makes it possible to examine them in detail. The movements of the eye are carried out without the participation of consciousness and are objectively unnoticed by a person unless attention is turned to them.

Thanks to habit the eye also fails to notice one further circumstance, namely that a definite part of the retina takes no part in vision at all and is blind. This is the region immediately adjoining the exit of the optic nerve. In this part of the retina light-sensitive elements are entirely absent, and therefore light stimulation cannot be received: it is called the blind spot (punctum caecum). The blind spot spans an angular extent of approximately 6 degrees horizontally and 8 degrees vertically.

The great difference in the structure and in the area of distribution of the two types of light-sensitive elements, the rods and the cones, suggests that they perform two different functions in vision. This view was advanced by von Kries in the theory of “duplicity” he created: the cones serve to receive strong stimulation only, for “daylight” vision. Weak stimuli do not act upon them. At the same time the cones perceive the different colours.

The rods, extremely sensitive to light stimulation, begin to respond to it while there can be no question of the cones being excited; they are adapted to “twilight” vision. When the illumination of the retina is too great, all the visual purple in that place bleaches and the reaction of the rods ceases; the cones have already come into action in their stead.

In contrast to the cones, the rods, according to von Kries, lack the ability to perceive differences of colour, although their sensitivity to different colour stimuli is not the same.

Von Kries's theory is almost universally accepted in the physiology of vision and is confirmed by a great many observations and data. It must be pointed out, however, that some physiologists do not agree with it and adduce facts that contradict it.

If von Kries's theory may nonetheless be considered correct, there follows from it the consequence that the eye possesses two entirely different apparatuses for receiving light stimulation. At sufficiently high (“daylight”) brightnesses the central, foveal vision operates (in the fovea there are no rods at all and only cones), accompanied by fixation of the objects examined and fine discrimination of detail and colour; at low (“twilight”) brightnesses the peripheral apparatus of the rods operates, fixation ceases, detail is poorly discriminated and colours are not perceived.

In passing from high brightnesses to low ones the eye requires a certain, sometimes far from short, time to adjust to the new conditions. Thus, for example, if the eye was initially dealing with high brightnesses, the cones were at work, the rods were dazzled, the rhodopsin was bleached, and the black pigment had penetrated the retina, screening the cones from light. If the brightness of the visible surfaces suddenly becomes many times smaller, then first of all the aperture of the pupil will widen, admitting a greater flux of light into the eye, the black pigment will begin to withdraw from the retina, the rhodopsin will be restored, and only when enough of it has gathered will the rods begin to function. Since the cones are not at all sensitive to very low brightnesses, at first the eye will discriminate nothing, and only gradually, over a number of minutes, will the new mechanism of vision come into action, the full development of its capacities in the new conditions usually requiring from half an hour to an hour. The reverse series of phenomena occurs on a sudden transition from darkness to high brightnesses in the field of view. This adjustment of the eye to changing conditions of brightness is called adaptation.

It has thus been established beyond doubt that the result of the action of light upon the pigment discovered in the rods (“rhodopsin”, or “visual purple”) is a chemical process which transmits the excitation along the optic nerve to the brain.

These facts allowed the physiologists who investigated the vision and the eyes of fishes and animals to conclude that the duality of structure of the light-sensitive parts of the retina conditions a duality of vision itself: that the foveal central part serves for daylight vision, working under strong illumination, is marked by exact clarity and takes in much detail, while peripheral vision serves for “twilight” vision. It perceives in summary fashion, without detail, indistinctly, but is uncommonly sensitive to weak light. Physiologists further suppose that colours are perceived by foveal vision, while peripheral vision is supposedly deprived of colour perception.

The description of the properties of the light-sensitive elements of the eye belongs to its physiological structure. Let us recall some further facts of the same order. Visual sensations are excited chiefly by the action of light rays passing through the optical system of the eye, but light sensations in the eye may also be produced, as Helmholtz points out, first by mechanical pressure on the eyeball, and further by an electrical discharge, which produces a sensation of light. At the base of all the causes producing a sensation of light in the eye lie physico-chemical processes in the salt solutions in contact with the nerve tissue of the eye.⁵ These last phenomena can be observed with the eyes closed. In an open eye exposed to light a physico-chemical process takes place, consisting in a change in the concentrations of the salt solutions in the nerve tissues, in the bleaching of the pigment of the light-sensitive elements and so forth; but once the action of light ceases, that is, when the eye passes into darkness or closes, these chemical processes run in the reverse direction: the pigment is restored, the products of the chemical action diffuse, the concentrations of the salt solutions return to their normal state, and so on. These processes in the closed eye also produce light sensations. Among such sensations are the so-called after-images (Nachbilder).

The optical system of the eye is linked to the higher nerve centre, that is, the brain, by the optic nerves, and this link, given that a person has two eyes while the brain consists of two hemispheres, is realised in a particular way, which may be seen from the accompanying schematic drawing.⁴

The light-sensitive elements of the retina of each eye are served by nerve fibrils which unite into three bundles in each eye, corresponding to three groups of light-sensitive elements. Group I, lying on the right (temporal) half of the retina of the right eye, is united in one bundle. Group II, that of the centre of the eye, containing the elements of the yellow spot and the fovea, is united in a separate bundle, and finally group III consists of the elements of the left (nasal) half of the retina of the right eye. All three bundles make up the optic nerve of the right eye. In the brain, at the so-called chiasm, this optic nerve meets the corresponding nerve of the left eye; here a redistribution of the nerve fibres takes place, and out of the chiasm there issue into the left and right hemispheres of the brain two trunks, called tracts. The redistribution of the fibres is as follows: the bundle from the temporal part of the retina of the right eye remains in the right tract and, uniting with the bundle from the nasal part of the retina of the left eye (group I of the left eye), goes to the right hemisphere. The bundle of group III (the left, nasal half) of the retina of the right eye crosses at the chiasm into the left tract. Finally group II, of the centre of the right eye and the fovea, divides, remaining partly in the right tract and partly crossing at the chiasm into the left tract leading to the left hemisphere.

L and R are the retinas of the left and right eye, on which light projects the images of the external world. NLE and NRE are the optic nerves of the left and right eye. Each of them, for example NLE, is so arranged that one of its two parts serves the left part of the retina of its own left eye, while the other of its two parts serves the left part of the retina of the other, the right, eye. The nerve of the right eye, NRE, likewise serves with one of its parts the right part of the retina of the left eye, while the other serves the right part of the retina of its own right eye. The nerves NLE and NRE cross at the point X (chiasma) of the brain, whose left and right hemispheres are marked LH and RH. In doing so a part of the nerve NRE of the right eye joins a part of the nerve NLE of the left eye and goes to the right hemisphere as the optic nerve of the right hemisphere, while a part of the nerve NLE of the left eye joins a part of the nerve NRE of the right eye and, crossing at X, goes to the left hemisphere as the nerve of the left hemisphere. Thus each eye has a nerve connection with each of the two hemispheres of the brain, and each eye separately reports the excitations of light on its retina to both hemispheres.

Having thus followed the apparatus of visual excitation as far as the brain, we must pass to those phenomena which run in our consciousness parallel with the excitations produced by light in the brain, through the optical structure of the apparatus and the physiological structure in the cerebral hemispheres. These phenomena, the so-called psychic ones, belong to the province of psychology.

Visual perceptions. The question nearest to the foregoing considerations in this field is how, given two separate images on the two retinas of our eyes, we see, in looking at the external world, only one picture of it. The usual answer is that the two retinal images “are superimposed one upon the other in the brain, and consciousness sees a single image”. But by closing first one eye and then the other one may notice that the images seen in the two cases are not identical, since objects which in one case are projected upon certain objects turn out in the other case to be projected upon quite different ones.

Vision with one eye and binocular vision are very different. With one eye one always sees, quite distinctly, the projections of some objects upon others; in binocular vision this is not so. In the brain, evidently, no superimposition of one image upon the other takes place; rather, each eye sends to the centre (the brain) the excitations from the images on its own retina, and at the centre each excitation is received separately but is realised as a representation of a single external world. To be conscious of the excitations of each eye separately, without closing the other, that is, to see with each eye separately, is possible only after long practice.

Our visual apparatus is so arranged that in binocular vision the contractions of the muscles of the eyeballs set them so that one point only of the external world casts its image on the fovea of both retinas. Such a position is called the fixation of the given point. From infancy the muscles of the eyes grow accustomed to shifting the position of the eyes so that both eyes always place the fovea of their retina under the retinal images of one and the same point in nature. This joint shifting of the eyes, so that any points of nature are projected successively but always simultaneously upon both foveas, is carried out without any difficulty, automatically, and belongs to all “examining”.

This joint shifting of the eyes in “examining” is performed so easily and unconsciously that it entirely conceals the indubitable fact that at any moment we see quite clearly only the one point of the external world that we are fixating. It is indeed not easy to convince oneself that a retinal image not falling on the fovea is received indistinctly compared with one that does, because as soon as the wish arises to establish this indistinctness at any place, the eyes at once shift involuntarily, placing the fovea under the place of the supposed indistinctness, and of course see it perfectly distinctly, while the place formerly seen distinctly passes into the region of the indistinct. A person is thus left in the conviction that there is no indistinctness in his vision at all. This rapid, easy gliding of both eyes over different points of nature, or in other words this successive placing of the fovea under different retinal images of points of nature, is precisely what proves that the whole periphery of the retina gives indistinct images, and that only the fovea perceives clearly.

The indistinctness of peripheral vision has three causes.

First, the so-called spherical aberration of the optical system of the eye; second, the fact that at the periphery of the retina the light-sensitive elements are less closely set than in the fovea and, moreover, that each element is not served by its own nerve fibre as in the fovea, but about 150 of them are served by one fibre of the optic nerve. The third cause, finally, is the convergence of binocular vision. Indistinctness from this cause, though by habit unnoticed by us, can easily be brought out. For instance, if one looks out of a window from two or three metres away at the glazing bar of the frame and then, without taking one's eyes off the bar, tries to attend to the object in the street on which the fixated bar is projected, one notices that this object doubles (that is, we see it simultaneously and separately with the right eye and with the left). If one then moves the eyes to that object and fixates it, and again, without taking one's eyes off it, attends to the window bar, the latter in its turn will double. The success of such experiments depends on whether the person performing them can, while fixating the far object, turn his attention to the nearer one without taking his eyes off the far one, and the reverse.

Thus only the fovea perceives distinctly the images of the external world projected on the retina, and our consciousness perceives these images distinctly by means of the fovea through a successive survey, part by part, in various directions, spending time on it. But it must not be forgotten that this survey is always accompanied by the constant presence of the whole retinal image spread over the whole periphery of the retina, and although this peripheral, indistinct perception escapes consciousness as something habitual, that perception from the periphery nonetheless has for us a quite definite and important significance. From the optical point of view, perception from the periphery of the retina is qualified as “coarse, devoid of detail”, “serving for rough orientation and not for vision in the true sense of the word”. From the point of view of our consciousness, however, that is, psychologically, visual perceptions from the periphery of the retina are one of the sensations of the three-dimensional space surrounding us and of our position with respect to objects in three-dimensional space, and also of the relative position of objects in space generally.

The periphery of the retina is uncommonly sensitive to the very faintest stimuli of light and to small differences between the stimuli of separate parts of the retina. This great sensitivity may be judged from the fact that the ratio of the greatest brightness the eye can bear (about 16 candles per square centimetre) to the least it can distinguish is 250 billion.³

For all the indistinctness of outline, that is, of the boundaries between the different illuminations of objects whose images fall on the periphery, these different illuminations, however slight they may be, are sensed by us, especially at the least movement of the objects or of the observer. Small differences in the illumination of objects are one of the subtle signs of an object's distance from the eye; add to them the least movements, disclosed by the great sensitivity to changes of illumination, and all this arouses in us the sensation of the space surrounding us and of its three-dimensionality. To take account of the third dimension of objects in seeing is the visual perception of form. The forms of the external world are perceived by us visually, first, through the sensation of the third dimension by means of the accommodation of the eyes, which lets us feel that different points of a plastic form lie at different distances from the eye; and second, simultaneously with accommodation, through sensations of light and shade upon the forms, that is, through the differing illumination of the parts of a form. Accommodation, that is, the change in the radius of curvature of the surface of the lens, is produced by the contraction of the muscles from which the lens is suspended, and these contractions give a “motor” sensation always bound up with the visual sensation of the three-dimensionality of form. How the play of light and shade brings out form we can make clear to ourselves by imagining that an illuminated flat surface will be seen as evenly lit; then every irregularity on that surface must necessarily cast a shadow, that is, disclose a breach of the plane, that is, disclose upon the plane the plastic form of the irregularity.

All the moments of experienced visual perception described here, namely the sensation of space itself, the sensation of the three-dimensionality of space, the sensation of the form of bodies, the sensation of light and shade, all belong to the working of that one of the two apparatuses receiving light stimulation which von Kries's theory calls the apparatus of “twilight”, or peripheral, vision. One cannot fail to notice that the light excitations furnished by this apparatus are experienced as sensations, often not even reaching consciousness, as producing unconditioned reflexes that give rise to feelings.

The apparatus of “daylight vision”, that is, the part of the retina of the yellow spot and the fovea, works otherwise from the psychological point of view. Each cone in the fovea is furnished with its own separate nerve fibre; in the yellow spot most cones have their own fibril; spherical aberration is absent; convergence in the fovea produces no doubling of the image, which is perceived clearly and sharply with all the possible abundance of minute particulars that the acuity of the given eye permits. The greater the acuity of vision, the smaller the details discerned in the fovea; the boundaries of contrast between different illuminations and colourings are followed with complete distinctness. And all these excitations from the fovea are experienced no longer as sensations merely, and sensations escaping consciousness at that, but are experienced psychically and distinctly by consciousness as cognition, as knowledge obtained by way of sight.

So if physiology, finding that the fovea works at high brightnesses, regards foveal vision as the apparatus of daylight vision and peripheral vision as the “twilight” one, since it is sensitive to faint light excitations, then from the psychological point of view we are entitled to ascribe to foveal vision the capacity to serve directly our cognitive faculty, our knowledge, and to peripheral vision the capacity to serve our sensations.

Let us further note that foveal vision, always fixating one point of nature after another, gives consciousness sensations in two-dimensional planes perpendicular to the axis of vision, leaving orientation in three-dimensional space and the sensation of “depth” to peripheral vision, which, functioning constantly, is in the visual field the same kind of apparatus as the semicircular canals of the ears, which report to us the sensation of our centre of gravity with respect to the force of gravity.

Much work by physiologists and psychologists has been devoted to the study of the relation between physiological excitations, light, and the psychic experience of them. Helmholtz's investigations in his physiological optics are especially important. Helmholtz studied these relations in visual perceptions both of the three-dimensional world and of two-dimensional diagrams and drawings, and points to a whole series of phenomena known as “optical illusions”. These optical illusions relate chiefly not to observations of the three-dimensional world but to drawings and diagrams on a plane, and consist in general in the fact that drawn lines or figures with definite geometrical properties are, under certain conditions, always perceived by us as if unquestionably endowed with other properties. For example, two strictly parallel lines always seem to us to converge if each of them is crossed at an acute angle by a series of short parallel segments, the segments crossing one line being at right angles to those crossing the other (the Zöllner experiment and others).

Of these optical illusions the one of greatest importance for the construction of a painting is the fact that two drawn figures of exactly the same size but of different colouring, especially if one is white and the other black, always appear to us to be of different sizes.

All these “optical illusions” are contradictions between the true size and shape of the object observed and the representations of size and shape that we receive in perceiving it visually. The causes of these contradictions lie, first, in the shortcomings of the optical structure of the eye, and second, in an eye that is faultless, in the erroneous appraisal by consciousness of the excitations passing from the eye to the brain, that is, in a psychic process. Munk was the first to point out that blindness may be physical, when the optical system of the eye is damaged, and psychic, when a subject with faultless eyes sees nothing owing to damage to the visual part of the brain. And this indicates that, whatever the given quality of the eyes, visual perceptions may psychically be perfected and developed in various directions.

Having taken account of all that has been set out concerning visual perception in general, we should turn to establishing the means that painting possesses for acting upon those perceptions. The process of visual perception is so habitual and familiar to us that we pay it no attention at all and do not suspect the enormous number of facts that go into it. By contrast, turning to painting, which presents so great a variety of kinds that a great number of means of expression is involuntarily assumed, we find on closer examination that these means are very few: there are only two, line and the tonal patch, and line is not even a necessary means, so that the one necessary and sufficient means is the patch alone. Every painted work may be regarded as an arrangement upon a plane of patches reflecting light from that plane in differing degrees. The boundaries between patches of different colour or different illumination present themselves in painting as lines. Line is a mathematical concept; in nature line does not exist, it is a fiction that can only be thought and not sensed. Line has one dimension and is defined in three-dimensional space as the intersection of two planes or surfaces. The depiction of a line on a plane, that is, the depiction that we sense by way of sight, is evidently not the line itself but a sufficiently narrow patch. Line is a concept that is thought; if we speak of a line that is sensed, that can only be the intersection of two surfaces, which we can touch, or else it is the depiction of a line.

To learn what significance and what role the depiction of line plays in painting, it is useful to look into the history of the development of painting for its origin. Since objects of a sculptural character dug from the various strata of the earth are found in older layers than objects with drawings engraved upon them, it may be assumed with confidence that sculpture must have appeared in human activity earlier than drawings. The whole external world consists of three-dimensional objects, and to repeat the three-dimensional form of an object of the external world in some material as a sculpture in the round is far simpler and easier than to give a notion of that same form by means of a drawing, that is, to give a notion of a three-dimensional form by means of a two-dimensional drawing. It should be noted here that a drawing fixes upon a plane one definite projection out of the infinite number of possible projections of a three-dimensional body onto a plane, and the finding and choosing of that projection is far more complex and difficult than the repetition of a three-dimensional form in sculpture in the round. The essence of sculpture in the round is that, in repeating or creating a three-dimensional form, the sculptor gives it to us entirely detached from the rest of the three-dimensional world and without any connection with it, to be perceived in the whole infinity of its aspects, by sight or by touch. This independence of sculptural forms in the round from the rest of the world is fully realised if we perceive these forms by touch; if we perceive a form in the round by sight, its connection with the surrounding world may express itself in the fact that it can be lit in different ways, from the left or the right and so on, and thus this or that lighting will bind the form to the external world in our perception of it. But this connection can be altered by us at will and is in no degree inherent in the sculptural form itself.

In painting the case is otherwise. In painting, what is conveyed is usually conveyed in connection with space and with the objects surrounding what is depicted. Painting usually depicts a part of the space of the external world with all the objects in it. All these objects are bound to one another and even to those objects which do not fall within the field of view of the depicted part of space: they are united by the depiction of the light that illuminates them, the colour of one object is reflected on another and so forth. Even if the artist wishes to depict an object on its own, without the surrounding space, that is, as it is said, “on a plain ground” or “without a ground”, even then it will be lit from somewhere, from the right, from above, and this will indicate how the object is connected with the rest of the world.

There is in painting one conventional means of depicting an object outside its connection with the objects and space around it, and it deserves attention, because it must have been the first that humanity found for depicting forms on a plane, after sculpture had repeated three-dimensional forms. That means is the depiction of objects or forms by a single line tracing the contour of the object. The sense of this means, and the kinship of its principle with sculpture, is that just as the sculptor in modelling a form sets it apart from everything else, so the artist in drawing the forms of the external world on a plane carefully separates them from everything upon which those forms are projected in space, observing their boundaries, their contours, and fixing them with a line. Line thus took the place of the primary and most important factor of drawing. In the art of painting line demarcates the forms of the visible world and breaks them into parts within the drawing; line is an analysing, differentiating means, which has usually seemed indispensable as the base on which painting was built, and which to this day many cannot do without. As an object perceived by sight, the depiction of a line in a drawing or painting is an object of foveal vision, on whose points both eyes converge and along which they glide, taking in and coming to know every particular of what is depicted. Line, directly through the fovea, lets consciousness know what is depicted. Line and the fovea serve knowledge and thought.

But lines are used in painting, and especially in drawing, not only for demarcation or contour, but also for the depiction of shadow, when they are laid more or less densely and so form a patch. In such cases these lines are technically called hatching. The use of hatching in drawings is extremely varied, and hatching may be laid in every possible direction. The direction of a hatch stroke in a drawing is of great importance. Any line can call up a notion of direction, and every movement is defined by direction. It follows that movement stands in associative connection with line. When a person looks at the external world, the eyes perform an endless number of movements in various directions; these movements may be divided into two groups. One consists of those movements by which the eyes take in some form, fixating it (that is, holding its image on the fovea) and moving along the outer and inner boundaries of that form. These movements are made for the work of the fovea, that is, for exact vision. The other group of the endless number of movements has the aim of bringing to the fovea those parts of the optical image which fall outside it, on the periphery, and which for some reason attract the attention of consciousness. This group of movements is excited, so to speak, on the initiative of the periphery.

James, in his Psychology, in the chapter on the perception of space (vol. II, p. 161), analyses these movements in detail and points out that every point of the periphery which has received a light excitation from a projected image, at the moment of attracting attention to itself, moves almost automatically toward the fovea, and in doing so traces, as it were, a line across the neighbouring light-sensitive elements of the retina on its way to the fovea. These lines are curves and, on James's supposition, are not the same in different individuals, and are not even always the same in the same person, but are always characteristic for each point of the periphery and are, as it were, the radius vectors of a system of polar coordinates whose centre is the fovea. These lines define the distance and direction between the fovea and the point of the retina attracting our attention, that is, the point to which our gaze is directed. All these movements are performed continuously and constantly while our eyes are open, and especially when a person drawing looks at the nature he is depicting. And if the eyes are offered drawings containing hatching and lines laid on the initiative of the fovea, of the periphery, and by chance, then the drawing in which the strokes are so arranged as to excite the eye movements habitual to it in perceiving nature will satisfy the viewer more than the drawing in which the strokes are arranged otherwise.

Here the lines that arise on the initiative of the fovea (contours and boundaries) will satisfy foveal vision and the viewer accustomed to working with that vision, while the varied lines and strokes arising on the initiative of the periphery will satisfy peripheral vision and the viewer who has developed it in himself.

Lines that satisfy foveal vision are recognised in drawings more easily, because in the visual perception of nature the process of thought is always bound to foveal vision, and a line consciously noted in nature is consciously carried into the drawing and is therefore more easily identified; whereas peripheral vision is bound to sensation, which for the most part remains in the region of the unconscious, and the lines that are its product can be identified rather by a negative route, that is, they are the lines which do not definitely serve foveal vision.

The other means of expression in painting is the patch, that is, areas on the canvas or paper which reflect light differently from the surface to which they have been applied in paint. These patches, contrasting with one another or passing imperceptibly from one intensity of reflection to another, create in their visual perception representations of plastic form. Patches in painting give us, on the plane of the picture, various illuminations analogous to the various illuminations of objects in nature which in nature make it possible for us to see and to know the external world. These various illuminations observed in the external world are called chiaroscuro, and in the external world this distribution of light and shade changes ceaselessly and continuously, on the one hand under the influence of changes in lighting and on the other from all the movements and displacements of objects and of the viewer. But at any given moment light is so distributed that in the field of view of a person looking at nature there is only one place (or point) of maximum illumination and only one of minimum, while all the remaining parts of the visible scene reflect light in quantities lying between them.

Theoretically light is always distributed in this way at any given moment within the visible field of view. These distributions of gradations of illumination usually go unnoted by people and only rarely arrest their attention at all, but for the artist it is very important to take them into account, and in the artist's visual perception of nature they are a constant object of his observation. These distributions of light are taken in through the working of the peripheral part of the retina, whose light-sensitive elements respond to the least differences of illumination.

Anyone who has tried to catch the true gradations of light in nature, that is, to take account of chiaroscuro, knows that in observing, say, the smooth surface of a wall which appears evenly lit, one can detect the difference of illumination between one part of it and another not while the fovea runs over the surface of that wall; the differences of illumination are disclosed when, fixating one point on the wall, one tries without taking one's eyes from it to attend to the whole surface. Then it becomes clear to peripheral vision which part of the wall is in fact more strongly lit than another. To convey the plasticity of forms in painting one must arrange the gradations of reflectance according to the intensities of illumination that define the forms of nature at the chosen moment. (Painting can depict one moment of time only.) In painting this distribution of gradations of intensity of illumination is usually called “holding the chiaroscuro”, and the means to it is the patch of differing reflectance, that is, the choice of intensity of colouring for the patches that make up the image on canvas or paper. To hold the chiaroscuro, to hold the valeurs (French valeurs), to hold the tone (from the German), is what all artists strive for, but they have achieved it in differing degrees. Not everyone feels and understands how far these gradations of chiaroscuro may be carried. In painting this carrying-through of gradations is achieved through the work of the artist's peripheral vision. In the viewer, too, peripheral vision excites immediate sensations, parallel to which consciousness experiences representations of the three-dimensionality of form and of space, and of the mutual placing of these forms in space.

Painting, then, possesses these two means of expression, line and patch, for conveying visual perceptions from one subject to another. Visual perceptions are excited by light reflected into the eyes from the forms of the external three-dimensional world. Painting seeks to convey the representations created by visual perceptions of the three-dimensional world through the visual perception of light reflected from the plane of the picture or the paper, regulated by means of lines and patches on that plane. The first task here is to convey the three-dimensionality of form upon a plane. Both line and patch exert themselves in this, but each of these two means strives toward its goal differently, according to its nature and its properties. Line in the sense of contour gives the projection of a form onto a plane of two dimensions, but line is not deprived of the possibility of hinting at the three-dimensionality of a form, or even of depicting a form in three dimensions, by giving the measurements of the third dimension, that is, of depth, in foreshortened form, in perspective. This conveying of one of the three dimensions in a certain “foreshortened” form has the character of something arbitrary, and exact thought and knowledge, which foveal vision and line both serve, cannot bear the arbitrary; and so exact thought, the inquiring mind, invents a system of these “foreshortenings”, that is, perspective, building it on the basis of descriptive geometry, an exact mathematical science. But it cannot be concealed that the whole scientific exactness of this perspective exists only on condition that perspectival images are perceived with one eye, while in binocular vision its exactness turns into approximation. This is why some artists, for all their respect for science, unwilling to renounce their natural right to receive sensations of the external world with two eyes, are inclined in their painting to disdain the exactness of the rules of perspective.

So line as contour, line lying at the base of perspective, perceived through the fovea, is able to express three-dimensional form in painting by giving it to be known through thought. The patch in painting, as chiaroscuro, gives the representation of the three-dimensionality of forms through immediate sensation.

So far we have touched on “colour” neither in analysing visual impressions of nature nor in analysing the means of expression in painting, for this reason: although colour plays an enormous role both in visual perception and in painting, and although much scientific work has been devoted to its study, colour is nonetheless known to us as a subjective sensation, and physiologists are only feeling their way toward objective explanations of it. From personal experience I cannot agree that peripheral vision, that is, vision by the rods, does not sense colour, in contrast to vision by the cones in the fovea, and I think that most artists sense colour with peripheral vision as well. Remaining, however, on objective ground, let us mention only one characteristic phenomenon in the visual perception of colour. When the eyes of a person looking at nature run over various forms, variously lit and variously coloured, then upon each part of the retina fall rays of the most varied brightness and of different colours, in the most varied succession. The duration of the light stimulation of each part, when images on the retina change rapidly, lasts somewhat longer than the change of image itself. Thus, for example, a part of the retina just now affected by red rays may receive the stimulation of blue rays while the action of the red has not yet ceased. And this happens always, in every visual perception; but of course only artists can notice that within any given colouring of an object other colours “seem to appear”, and only those among them who in their works seek to give the viewer sensations analogous to those received from nature, rather than the knowledge that some object is painted in such and such a colour.

For example, in depicting a smooth, clear, blue Italian sky, an artist who has satisfied himself of all these visible qualities of the southern sky wishes to convey them in his painting, chooses paints of a suitable colour, lays that paint on the canvas with the greatest care, diligently observing the visible gradations of saturation, and smooths out every unevenness of the paint. And the viewer, having examined all the care of the work, says: “How beautifully the transitions of the sky are done; this really is an Italian sky, clear, smooth, blue.” Differently works the artist who in his picture seeks to convey the sensations received in the visual perception of an Italian sky. He knows that the sky is clear and smooth, but in looking at it, by virtue of the natural structure of the eye already described, he takes into account not only the known properties of the colour of the sky but also the properties of the eye which always accompany the sight of any viewer, and he brings into his depiction of the sky not only the depiction of the properties of its colour but also traces of the properties of the eye, for which purpose he writes into the colour of the sky all the colours which, for the reasons set out above, “seem to appear” when one looks at it. And the viewer may of course see all manner of colours in the blue tones of the sky if, as they say, he buries his nose in the canvas; but looking at the picture from a proper distance, and paying them no attention, he says: “A real Italian sky, you can positively feel its light, its clarity and even the warmth of the south.” This example brings us to an important moment in our study of the relation between visual perception and painting, namely to the following question. If painting is born of visual impressions, is all the varied painting known to us built on the principle of correspondence with the processes of visual perception or not, and if in correspondence, then in what degree and in what does it show itself?

The answer in broad terms will be that among the enormous variety of paintings there are some which are calculated, within the most modest limits, to produce impressions corresponding to those we receive in visual perception from nature, and whose aim is not to arouse sensations analogous to visual perception but rather, by means of conventional depiction, by ways more literary than plastic, to give notions and information about what is depicted. In the remaining works there is an unmistakable wish so to use the means of painting that their action on sight should correspond to that which sight receives from nature. In these works this correspondence is carried through more or less consistently in two directions. The character of the one direction in which this correspondence of the language of painting with the process of visual perception is carried through consists in bringing into that painting all the means that lead to the satisfaction of knowing what is depicted; the other direction consists in bringing in those means that lead to sensation, that is, to the viewer's feeling the image immediately before him as if he were receiving a visual impression not from the image but from nature itself. Thus, if we look at all painting as experience gives it to us, that is, at all works made by man with paint on a two-dimensional surface, then by execution they divide into those which either wholly or largely renounce the carrying-through of correspondence between their means of expression and the conditions of visual perception, and those which strive toward it. For clarity let us note what may be understood by this “correspondence”. For example, visual perceptions give us representations of the forms of the external world always coloured in all the colours of the spectrum, whereas a drawing or a painting may convey those same representations in a single colour (achromatically, in black and white). Such a choice of means already diverges from the correspondence spoken of. A drawing of some objects may be given in contours alone, without shadow, and here the divergence from “correspondence” is greater still. If we depict a rapidly turning wheel and draw in all its spokes, that depiction will correspond to the true construction of the wheel but will not correspond to the visual perception of a rapidly turning wheel, in which the spokes are not seen. From this it is clear what may be meant by defining paintings as deviating in their construction from the carrying-through of correspondence with visual perception. In the remaining works this correspondence is carried through more or less deeply, and those works in which it is carried through with the aim of satisfying chiefly, or in the first instance, the cognitive need, have a “graphic” character, while those which reckon to act from the first moment upon sensation may conveniently be called painterly.

Having touched upon these two expressions, “graphic” and “painterly”, that is, upon the opposition of graphic art to painting, I permit myself to dwell on these terms, which carry within them the definitions of two different ways of conveying experience and thought from one consciousness to another. In everyday use these expressions are understood easily and simply, but on closer examination the matter proves more complex. Etymologically the word “graphic” points to “inscribing”, while in the Russian word for painting, zhivopis, from “to write vividly”, there is a pointing toward the striving to depict vividly, in a lifelike way, that is, in correspondence with the representations received from nature. The most characteristic difference between graphic art and painting is that painting strives to use every means in order to depict in a lifelike way, whereas graphic art consciously or unconsciously deprives itself of one means or another for one purpose or another. The primary aim of both graphic art and painting is to call up representations in consciousness. Representations, as is known, are singular and general. Singular representations are those by which are taken in the features of the represented objects that belong to that definite object and constitute its difference from the rest. General representations are those which, in psychology, give us the features equally belonging to a whole group of objects. A singular representation would be the representation of the house in which you live. It is a wholly definite house, and all its features distinguish it from other houses. The representation of a house without further definition will have the features common to houses in general, and this representation is called in psychology a general representation. Logic recognises that general judgements, operating with general representations, are of greater significance for the widening of knowledge. Painting calls up representations, and these representations may approach either the singular or the general, depending on how the depictions are carried out. I. E. Repin depicted in one small landscape L. N. Tolstoy ploughing. Lev Nikolayevich is depicted with a strong likeness and with all his features, so that in the viewer there arises the representation of Tolstoy ploughing, and this representation is singular; but the same Repin might have wished to depict simply a ploughman, without individualising him, and so to give a representation of a ploughman which would already be “general”. In one and the same picture an artist may depict a scene with a number of people, of whom he individualises some as being of importance to him and generalises others, wishing merely to indicate that “people” were present at this scene, and thus makes the representations of the first singular and of the second general. To achieve this in painting everything comes down to giving a greater number of individual features in order to bring out singular representations, and to reducing the number of features in order to bring representations closer to the general (closer to the general, because general representations do not exist without the singular). Thus in a portrait painted in colours it is possible to realise singular representations most fully, since painting possesses the greatest number of means for conveying the full visual perception of the person depicted. On the other hand graphic art, because it itself renounces one means of expression or another and thereby reduces the number of individual features, is the more capable of calling up general representations.

But it must be borne in mind that graphic works in the accepted sense of the word may be built on a purely painterly principle, as for instance all the drawings of Rembrandt, and equally that paintings may be executed on a purely graphic principle, as for instance the painting of Dürer.

That a work belongs beyond doubt to the graphic order is revealed by the presence of three properties: 1) a reduction of the means of expression, that is, the renunciation of colour, or of chiaroscuro, or of perspective; 2) the reduction, bound up with that limitation, of the number of features of what is depicted, which leads graphic art toward the capacity to form general representations; and finally 3) the property of the graphic principle of acting upon consciousness in the first instance through thought.

The properties of the painterly principle consist in the application of the maximum possible number of means of expression, leading to the best formation of singular representations, and finally in the fact that the action of the painterly principle upon consciousness lies in arousing immediate sensation to the utmost, leaving all the subsequent work to thought. These two principles lie at the base of the technique of executing paintings, according to the character of the artist, that is, to the organisation of his habits. And these habits are worked out from bringing the habits of visual perception into correspondence with the means of expression in painting.

Strictly speaking, this realisation of “correspondence” between visual perceptions and the arrangement of the material forming a painting, which in its turn is to serve as an object of visual perception, is precisely the art of painting. The technique of painting consists in carrying this correspondence through, and by “technique” is meant here not only the care for paints and their mixing, the action of one paint upon another, for canvas, paper, varnish, oils and other liquids in which paint is thinned, for pencils, charcoal, priming, underpainting, washes, sinking-in and the rest; besides all this, the concept of technique includes the principles that guide the practical application of the knowledge of these things, that is, for example, the choice of what is to be depicted, in what arrangement the separate parts will stand, how the depicted three-dimensional space will be organised, the choice of lighting, what is to be at the centre of the viewer's attention, by what means the action upon the viewer will be realised, that is, whether he is to sense the depicted by way of sight and then, with the associations arising simultaneously with the sensations, receive food for thought, or whether he is to receive by way of sight much exact information about what is depicted, knowing which he may think and, in accordance with what he has come to know, feel. In the choice of these technical means, that is, of these or those guiding principles, the personality of the author of a painting is expressed, and the acquisition of the habit of applying such a technique is for every artist the necessary condition of his skill, of his art. The acquisition of these habits constitutes the whole “teaching” of the art of painting. Much energy and stubborn labour is spent on the work of acquiring them during the period of “study”; each carries this work on in his own way, by feel, and where people work together, in academies, studios and schools of painting, there are always endless conversations, arguments and discussions among students of the most varied character on the most varied themes: on drawing, chiaroscuro, paints, colouring, warm and cold tones, half-tones, hatching, brushstrokes, all manner of devices and means of every technique, material and principled, that is, creative. And all of this is in its very essence a search for the habits of arranging material on a two-dimensional surface in such a way that the visual perceptions it arouses either correspond or do not correspond to the perceptions received from the three-dimensional world. All “study” and all “searching” has this for its object, until each, achieving it either by his own experience or at second hand, settles into some habit that more or less satisfies him, a “style”, in which he comes to rest and which he then exploits, or else varies and perfects to the end of his days. Given the enormous variety of individualities, the results achieved are very various too, but in essence all this labour of working out one's own skill in painting or drawing amounts to the same question: how to develop one's capacity for visual perception and how to bring one's means of painterly expression into accord with it. In the choice of his technique there is expressed not only the personality of the artist but also the primary aim of each of his works. That primary aim may be to communicate the most exact information possible about what is depicted, or to give what is depicted in such a way that the viewer may sense it before him. Of course both aims are always pursued together, but the centre of gravity may lie in the one or the other.

If out of the whole number of existing and most varied paintings we seek out and select those which most stubbornly and consistently pursue the aim of giving the viewer as much exact information and detail as possible, and then set them in a row with other works in which this aim is pursued less insistently while another aim appears at the same time, that of giving the viewer sensations, an aim which gradually gains preponderance, then we obtain a series at one end of which stand architectural and engineering drawings, then works containing all the intermediate combinations of the one aim and the other, and finally, at the other end, paintings of an impressionist character. And if within this series we group the works pursuing predominantly the one aim, then those pursuing both together, and finally those pursuing predominantly the second aim, then within each of these three groups the works may in turn be arranged in perpendicular rows according to how close they are in execution to those pursuing the “correspondence” with visual perception spoken of, or close to those deviating from that correspondence or denying it.

Let us now look at the construction of the painting in which this correspondence is carried through, how it may be carried through in painting, and in what it is expressed. To carry through a correspondence in painting between the visual perception of the two-dimensional surface of the painting and the visual perception of the three-dimensional world means so to arrange the material (the paint) over the two-dimensional surface that, on offering it to sight, one calls forth in the visual apparatus as far as possible that same work of the apparatus which is inevitably and always performed when sight perceives the three-dimensional world. Here one must at once recall that our visual apparatus works with two sorts of light-sensitive elements, the group of the yellow spot with the fovea and the group of the periphery, and that these two groups, working together, may nonetheless produce excitations unequal in intensity. In other words, in looking at the three-dimensional world the viewer's eyes may work predominantly either with the periphery or with the fovea. And in painting one may likewise offer work predominantly either for the fovea or for the periphery, according to the primary aim. In carrying through a correspondence with visual perception where the aim is to give more information, one must give the eye the work by which it takes in every particular in the space of the field of view, analysing, demarcating and coming to know; and then vision concentrates on the activity of the fovea, guided by thought. And in painting, line is the surest means for this, leaving nothing unsaid for the fovea over the whole field of the image. But in carrying through a correspondence with visual perception where the aim is to give the eyes that work in which sight orients itself at once in space, senses its three-dimensionality and the mutual relation of three-dimensional forms, that work in which sight gives the sensation of a three-dimensional world before it, that is, makes considerable use of peripheral vision, then in painting too one must, as far as possible, arouse by the arrangement of the material that work of sight which is most nearly founded on sensation, that is, on the muscular sensations of movement in the eye and on the sensations of light and colour. In the visual perception of nature, in looking at nature, the visual process is experienced as follows: the work of the fovea proceeds in time more or less rapidly and is always accompanied by the work of the periphery. The work of the fovea may draw the attention of our consciousness to itself in greater or lesser degree, but in seeing, the periphery always guides foveal vision, leads it after itself, however strange this may seem. The fovea converges the eye upon a definite point lying at a definite distance from the eyes. The periphery, on the other hand, orients our consciousness at once with respect to our position in space and to the mutual position of ourselves and the objects of space, and then, thanks to its uncommon sensitivity to the least differences of illumination of parts of the retina arising from the least movements in nature, draws the attention of our consciousness to them and at the same time leads the fovea to new fixations, that is, guides the movements of the fovea. For example, you are looking at a building deep within a rural landscape, but the least stirring of the grass at your feet, caused by the movement of a frog, will instantly draw your gaze, that is, your fovea, to the ground at your feet. Or, examining any object in a room, you will unfailingly shift your gaze to a moth flying through the field of peripheral vision. In general, in examining what stands before the eyes in nature, moving the fovea over the whole field of view, these movements of the fovea rush after the excitations experienced by the periphery, which can react to weaker actions of light than the fovea, less sensitive as it is to weak stimuli.

Thus the whole work of the eye consists of muscular contractions and movements furnished by convergence at changes of the point of fixation, of sensations of light and colour accompanied by fine adaptation, the muscular movements in adaptation being furnished by the contraction or expansion of the diaphragm (the iris). This complex work of the visual apparatus is always present, is always performed by its mechanism purposefully and exactly, passing the results of its excitations to the discretion of consciousness and to further reflexes. The work itself, having entered the region of habit, goes wholly unnoticed by us. No one thinks that at every glance he must change the radius of curvature of the lens, or change the angle between the axes of vision of the eyes, or place the fovea under those places of the retinal image which need to be examined more exactly than the indistinctly seen parts of the periphery, or adapt his vision at points of excessively strong or excessively weak illumination. Yet this work is necessarily performed in the visual perception of the three-dimensional world, and it is precisely this that establishes for consciousness that before the eyes lies a three-dimensional space with three-dimensional objects and with all the movement taking place within it.

By what means, then, is all this work of the eyes to be called forth when one offers them the two-dimensional surface of a painting; how is the material to be arranged so that the eye must perform all this work, that is, how is the “correspondence” spoken of above to be carried through? Of course the whole of this work cannot be given to the eyes by painting, but part of it can be given, and another part can be stimulated, an impulse given for its performance. Chiefly, the chiaroscuro must be held with the utmost care, that is, light and shade must be so arranged that there is one place only of maximum illumination and one place only of minimum, all the remaining places being intermediate gradations. Further, by no means over the whole surface should all the details be clearly executed, so that the eyes may meet those indistinctnesses which in nature always occur at changes of fixation from one point to another, changes arising from the fact that all points of the three-dimensional world lie at different distances from the eyes. Meeting indistinctnesses in a painting, the eyes at once receive a stimulus to accommodation and convergence, and partly perform them, and the muscular sensations obtained correspond to the habit of perceiving three-dimensional space. Colours act in the same way if they are laid on unevenly, not according to the colouring of objects in nature but according to how the eyes perceive it under constantly changing colour stimuli. By these extraneous tones the eyes are given an impulse to make out the colour as they do in looking at the three-dimensional world. In places strongly lit, in highlights, the exactness of drawing must disappear and the surrounding details be lost, which likewise makes the eye work at adaptation, when the acuity of vision in the regions of the retina neighbouring a strongly lit patch is weakened.

All these means in painting lead to calling the eye to that work which is performed in the visual perception of the three-dimensional world, and give painting the character of “painting”, giving sensations close to those aroused by looking at nature.

All these departures from truth in painting so constructed call up truer representations than are given by painting that is truly documentary. This is precisely that “artistic truth”, so often cited by critics, which is set against “real truth”.

1. James, Psychology, vol. I, ch. XIII, p. 487
2. I. P. Pavlov, The Physiology of Higher Nervous Activity, in Priroda, 1932, nos. 11-12, p. 139
3. S. Maizel, Light and Vision, Leningrad, 1925, in Transactions of the State Optical Institute, vol. IV, part 33, p. 41
4. See the photocopies of E. O. Wiesel's drawings below
5. P. P. Lazarev, The Ionic Theory of Excitation, Moscow, 1923

Wiesel's drawings for the report, diagrams of the eye and of the cerebral hemispheres, survive separately: Archive of the Russian Academy of Arts, fond 37, inv. 1, file 20, sheets 167-168. Photocopies of them are reproduced in the appendix to the dissertation.

Since his appointment in the summer of 1928, Emil Oskarovich Wiesel, Assistant Keeper of the Department of Drawings of the State Hermitage, has been engaged throughout in intensive research work on the material of that department. A major specialist in the art of the modern period, possessing both extensive theoretical knowledge and great museum experience acquired during his long years in charge of the Museum of the former Academy of Arts, E. O. Wiesel carries out in the department independent and responsible work on the sorting and scholarly systematisation of the drawings of the West European schools of the nineteenth century, on the checking of their attributions and the identification of anonymous sheets. In connection with these studies he has lately been preparing for the press an article on an unknown suite of works by Raffet which he discovered among the drawings of unknown masters. Taking part alongside this in the department's other research work, E. O. Wiesel has also occupied himself with questions of Marxist art history and has read a paper to the Scientific Society of Marxists. His activity over the same period has also found expression in the continuation of his large scholarly work “On visual perceptions and their connection with painting and the graphic arts”. This work, the first to use the current scientific data of optics and physiology to elucidate a series of artistic problems, has over recent months been in preparation for the press by E. O. Wiesel and will constitute an entirely new and exceedingly valuable contribution to the literature of art history.

Keeper of the Department of Drawings of the State Hermitage, Professor of the Leningrad Higher Art and Technical Institute, full member of the Institute of Art History /M. Dobroklonsky/

Over the past two years, that is, over the whole period of the work of the Fine Arts Section of the Scientific Society of Marxists, Emil Oskarovich Wiesel has taken an active part in the sittings of the Section, although he was not a member of the Society. In 1928 he read a paper to the Section on “Visual perceptions and painting”, which aroused great interest both by its framing of the question and by the strictly considered method of its solution. By the unanimous wish of the Section, E. O. Wiesel was invited to give a further communication on the problem he is working out, when, in completing his work, he should come to conclusions of both a theoretical and a practical order.

This work is now all but finished by E. O. Wiesel. It is beyond dispute evidence that E. O. Wiesel, besides the scholarly character of his official duties, has also carried out a special piece of research entirely new both in the theme taken up and in its resolution.

Chairman of the Fine Arts Section of the Society of Marxists, S. K. Isakov

Present: K. M. Bykov, G. S. Vereisky, E. G. Lisenkov, A. I. Aristova, F. Brandto, T. D. Kamenskaya, S. M. Zarudny, O. A. Fe, N. N. Punin, A. A. Sidorov, Dakhnovich, E. O. Wiesel, E. M. Lippold.

Chairman, E. G. Lisenkov. Secretary, E. M. Lippold.

Theses of the paper

Visual perceptions, like all others, consist of sensations and of the thinking inseparably bound to them. Either of these components may in perception prevail at the expense of the other.

The eyes possess two groups of light-sensitive elements differing in structure and function. The excitations of the group lying at the centre of the retina furnish exact vision, which differentiates and gives material for thought. The excitations of the other group, spread over the remaining space of the retina, furnish sensation in general and the sensation of three-dimensional space. The centre withstands strong light. The periphery is sensitive to weak light.

The content of thought can be transmitted exactly from one consciousness to another. The content of sensations cannot be transmitted directly from one consciousness to another, but is experienced by each in his own way.

Painting, being in its turn an object of visual perception, brings out its content by two means of expression: 1) the depiction of lines, 2) the patch. Line is perceived by central, foveal vision, while the quantity of light reflected from the surface of the painted work, which defines the forms, is appraised chiefly by peripheral vision.

Lines in painting are boundaries which differentiate what sight perceives in the painted work and give material to thought. The patch, in distributing the light and colour reflected from the painted work, arouses sensations in the viewer.

The thinking side of perception is active and always inclined to check the exactness and correctness of its own activity by logic. Sensations in perception, on the other hand, are experienced passively and determine the attitude of consciousness to the sensation, whether that attitude is positive or negative.

In painting, line, as the means of expression giving material chiefly for thought, when it tries to express three-dimensional forms submits to the rules of linear perspective, worked out by thought on the foundations of descriptive geometry. The perception of the patch, as a sensation of light, is experienced passively; the patch in painting serves to depict chiaroscuro, that is, it seeks to mislead sight by giving on a two-dimensional surface an impression such as comes from three-dimensional forms, and submits to aerial perspective, sensed by binocular vision.

Different types of people experience their visual perceptions differently. Different artists make different use of visual perception in creating their painting. Artists in whose perceptions thinking predominates are guided chiefly by central vision, and in painting by linear forms of expression. Artists who respond more strongly to sensation in their perceptions add to central vision, in greater measure, the data furnished by peripheral vision, and in painting make use of the patch in conveying the sensation of chiaroscuro.

Discussion of the paper

N. N. Punin observes that the main propositions of E. O. Wiesel's communication coincide entirely with the results of the laboratory's work. But in connection with the propositions of the paper a question arises: how is the relatively dark, brownish colour of pre-impressionist painting to be explained? Possibly this is bound up with the manner of seeing. Central vision looks at colour with concentration, complementary colours are laid one upon another in succession on the yellow spot, and the result is a brownish colour. Widened, or peripheral, vision makes it possible to perceive colour better and more distinctly, since in that case it is not shadowed by complementary colours.

E. O. Wiesel objects that central vision, on the contrary, defines colours clearly. Central vision serves cognition, and the knowledge obtained by a subjective route becomes objective. All artists up to a certain point work with central vision, but if an artist is able to take account of his sensations he will strive to develop that capacity, to develop peripheral vision.

K. M. Bykov observes that in the language of physiology the two concepts, central vision (serving knowledge, in E. O. Wiesel's terminology) and peripheral vision (serving sensation), merge and differ only in that central vision possesses the greatest differentiation of properties and peripheral vision a weaker one. Thus the intensity of the process of stimulation differs, but the role of rods and cones is the same. These two manners of seeing, these optic nerves, are joined in different sections of the cerebral cortex, and it should be noted that the optical region of the brain is not the only one in the sense of receiving light stimulation. Physiology stands on the point of view of objective cognition, and as yet there is no objective physiological knowledge of a functional difference between central and peripheral vision: we see not with rods or cones but with brain cells.

E. O. Wiesel replies that objectively the difference between the results of central and peripheral vision is evident. Lazarev, asked whether two manners of seeing could be established in two individuals, answered that they could. Neither the physiologists (Helmholtz) nor the psychologists (James) have resolved the question of the visual perception of the three-dimensionality of space, whether that perception is innate or an acquired habit; but it is worth noting that the three-dimensionality of an object cannot be taken in by one agent alone, and that evidently both act, both kinds of vision are at work.

K. M. Bykov replies that the process of perceiving space is a complex reflex process in which a multitude of muscles of the whole body take part. This becomes clear if certain areas of the cerebral cortex are excluded. Magnus, the Dutch physiologist, showed how Dutch painters in creating artistic forms unconsciously took account of a definite relation between the muscles of the body and of the eye. If Helmholtz in his day did not resolve the question, it was only because the question was not then clear and objective knowledge was lacking. E. O. Wiesel's terminology is at moments objective and at moments subjective, taking account now of physiological and now of psychic processes. There are no objections to the speaker's main propositions, but their interpretation from the point of view of physiology is somewhat different.

N. N. Punin observes that perception should be differentiated from the means of expression.

E. O. Wiesel points out that line is thought and the patch is sensed. All thinking can be transmitted, whereas sensation can only be called forth by material forms. In connection with this proposition the question arises of what art is, a question that might be resolved in the sense that under the term “art” there lies a particular human activity by which a sensation is transmitted from one consciousness to another, called forth by means of appropriately organised material.

N. N. Punin proposes not to draw a strict boundary between conscious and unconscious vision, but to keep to the terminology of central and peripheral vision.

E. G. Lisenkov closes the session, announcing that the conclusion of the paper and the discussion of it are postponed to the next occasion.

Chairman /E. G. Lisenkov/ · Secretary /E. M. Lippold/

The working materials for the paper, Archive of the Russian Academy of Arts, fond 37, inv. 1, file 20, remain unpublished.