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impatience, that this amounts to the monstrous absurdity of making the contents of consciousness extended. The edge of this objection will be best turned by rendering the conception of extensity more precise. Thus, suppose a postage stamp pasted on the back of the hand; we have in consequence a certain sensation. If another be added beside it, the new experience would not be adequately described by merely saying we have a greater quantity of sensation, for intensity involves quantity, and increased intensity is not what is meant. For a sensation of a certain intensity, say a sensation of red, cannot be changed into one having two qualities, red and blue, leaving the intensity unchanged; but with extensity this change is possible. For one of the postage stamps a piece of wet cloth of the same size might be substituted and the massiveness of the compound sensation remain very much the same. Intensity belongs to what may be called graded quantity: it admits of increment or decrement, but is not a sum of parts. Extensity, on the other hand, does imply plurality: we might call it latent or merged plurality or a “ground" of plurality, inasmuch as to say that a single presentation has massiveness is to say that a portion of the presentationcontinuum at the moment undifferentiated is capable of differentiation. Attributing this property of extensity to the presentation-continuum as a whole, we may call the relation of any particular sensation to this larger whole its local sign, and can see that, so long as the extensity of a presentation admits of diminution without the presentation becoming nil, such presentation has two or more local signs,—its parts, taken separately, though identical in quality and intensity, having a different relation to the whole. Such difference of relation must be regarded fundamentally as a ground or possibility of distinctness of sign—whether as being the ground or possibility of different complexes or otherwise—rather than as being from the beginning such an overt difference as the term “local sign,” when used by Lotze, is meant to imply." From this point of view we may say that more partial presentations are concerned in the sensation caused by two stamps than in that caused by one. The fact that these partial presentations, though identical in quality and intensity, on the one hand are not wholly identical, and on the other are presented only as a quantity and not as a plurality, is explained by the distinctness along with the continuity of their local signs. Assuming that to every distinguishable part of the body there corresponds a local sign, we may allow that at any moment only a certain portion of this continuum is definitely within the field of consciousness; but no one will maintain that a part of one hand is ever felt as continuous with part of the other or with part of the face. This we can only represent by saying that the local signs have an invariable relation to each other: two continuous signs are not one day coincident and the next widely separate.” This last fact is
say, as Mill seems to do, “that the idea of space is at bottom one of time” (p. 276), we must admit the inadequacy of our experience of movement to explain the origin of it. * To illustrate what is meant by different complexes it will be enough to refer to the psychological implications of the fact that scarcely two portions of the sensitive surface of the human body are anatomically alike. Not only in the distribution and character of the nerve-endings but in the variety of the underlying parts—in one place bone, in another fatty tissue, in others tendons or muscles variously arranged—we find ample ground for diversity in “the local colouring” of sensations. And comparative zoology helps us to see how such diversity has been developed as external impressions and the answering movements have gradually differentiated an organism originally almost homogeneous and symmetrical. Between one point and another on the surface of a sphere there is no ground of difference; but this is no longer true if the sphere revolves round a fixed axis, still less if it also runs in one direction along its axis. * The improvements in the sensibility of our “spatial sense” consequent on its variations under practice, the action of drugs, &c., are
hardly perhaps implied in the mere massiveness of a sensation, but it will be convenient to include it when speaking of the continuum of local signs as extensive. We have, then, a plurality of presentations constituting a continuum, presented simultaneously as impressions and having certain fixed and invariable relations to each other. Of such experience the typical case is that of passive touch, though the other senses exemplify it. It must be allowed that our conception of space in like manner involves a fixed continuity of positions; but then it involves, further, the possibility of movement. Now in the continuum of local signs there is nothing whatever of this; we might call this continuum an implicit plenum. It only becomes the presentation of occupied space after its several local signs are complicated or “associated ” in an orderly way with active touches, when in fact we have experienced the contrast of movements with contact and movements without, i.e., tin vacuo. It is quite true that we cannot now think of this plenum except as a space, because we cannot divest ourselves of these motor experiences by which we have explored it. We can, however, form some idea of the difference between the perception of space and this one element in the perception by contrasting massive internal sensations with massive superficial ones, or the general sensation of the body as “an animated organism” with our perception of it as extended.
It must seem strange, if this conception of extensity is essential to a psychological theory of space, that it has escaped notice so long. The reason may be that in investigations into the origin of our knowledge of space it was always the conception of space and not our concrete space perceptions that came up for examination. Now in space as we conceive it one position is distinguishable from another solely by its co-ordinates, i.e., by the magnitude and signs of certain lines and angles, as referred to a certain datum position, or origin; and these elements our motor experiences seem fully to explain. But on reflexion we ought, surely, to be puzzled by the question, how these coexistent positions could be known before those movements were made which constitute them different positions. The link we thus suspect to be missing is supplied by the more concrete experiences we obtain from our own body, in which two positions have a qualitative difference or “local colour” independently of movement. True, such positions would not be known as spatial without movement; but neither would the movement be known as spatial had those positions no other difference than such as arises from movement.
We may now consider the part which movement plays Movein elaborating the presentations of this dimensionless ment.
continuum into perceptions of space. In so doing we must bear in mind that this continuum implies the incopresentability of two impressions having the same local sign, but allows not only of the presentation of impressions of varying massiveness but of several distinct impressions at the same time. As regards the motor element itself, the first point of importance is the incopresentability and invariability of a series of auxilio-motor presentations, Pi, P., P., P. P. cannot be presented along with Po, and from P, it is impossible to reach P, again save through I’, and P. Such a series, taken alone, could afford us, it is evident, nothing but the knowledge of an invariable sequence of impressions which it was in our own power to produce. Its psychological interest would lie solely in the fact that, whereas other impressions depend on an objective initiative, these depend on a subjective. But in the course of the movements necessary to the exploration of
obviously no real contradiction to this; on the contrary, such facts are all in favour of making extensity a distinct factor in our space experience and one more fundamental than that of movement.
the body—probably our earliest lesson in spatial perception —these auxilio-motor presentations receive a new significance from the active and passive touches that accompany them, just as they impart to these last a significance they could never have alone.
It is only in the resulting complex that we have the presentations of position and of spatial magnitude. For space, though conceived as a coexistent continuum, excludes the notion of omnipresence or ubiquity; two positions /, and l, must coexist, but they are not strictly distinct positions so long as we conceive ourselves present in the same sense in both. But, if F, and F, are, e.g., two impressions produced by compass-points touching two different spots as l and l, on the hand or arm, and we place a finger upon l, and move it to l, experiencing thereby the series P, P., P., Pp this series constitutes l, and l, into positions and also invests F, and F, with a relation not of mere distinctness but of definite distance. The resulting complex perhaps admits of symbolization as follows:–
. . . . . Fa Fe F. F. F. Fr F, F. F. . . . . .
Pipa pap, Here the first line represents a portion of the tactual continuum, F, and F, being distinct “feels,” if we may so say, or passive touches presented along with the fainter
But in the evolution of our spatial experience impressions and positions are not thus presented apart. "We can have, or at least we can suppose, an impression which is recognized without being localized ; but if it is localized this means that a more complex presentation is formed by the addition of new elements, not that a second distinct object is presented and some indescribable connexion established between the impression and it, still less that the inpression is referred to something not strictly presented at all. The truth is that the body as extended is from the psychological point of view not perceived at all apart from localized impressions. In like manner impressions projected (or the absence of impressions projected) constitute all that is perceived as the occupied (or unoccupied) space beyond. It is not till a much later stage, after many varying experiences of different impressions similarly localized or projected, that even the mere materials are present for the formation of such an abstract conception of space as “spatial reference” implies. Psychologists, being themselves at this later stage, are apt to commit the oversight of introducing it into the earlier stage which they have to expound.
In a complex presentation, such as that of an orange or Intuition a piece of wax, may be distinguished the following points of things.
concerning which psychology may be expected to give an account:-(a) its reality, (b) its solidity or occupation of space, (c) its permanence, or rather its continuity in time, (d) its unity and complexity, and (e) its substantiality and the connexion of its attributes and powers. Though, in fact, these items are most intimately blended, our exposition will be clearer if we consider each for a moment apart.
(a) The terms actuality and reality have each more Actual
sensations of the continuum as a whole; T stands for the - than one meaning. Thus what is real, in the sense of "Yo
active touch of the exploring finger and P. for the corre- reality
sponding auxilio-motor object; the rest of the succession, as not actually present at this stage but capable of revival from past explorations, is symbolized by the t t t and 1, papt. When the series of movements is accompanied by active touches without passive there arises the distinction between one's own body and foreign bodies; when the initial movement of a series is accompanied by both active and passive touches, the final movement by active touches only, and the intermediate movements are unaccompanied by either, we get the further presentation of empty space lying between us and them,--but only when by frequent experience of contacts along with those intermediate movements we have come to know all movement as not only succession but change of position. Thus active touches come at length to be projected, passive touches alone being l, walized in the stricter sense. But in actual fact, of course, the localization of one impression is not perfected before that of another is begun, and we must take care lest our necessarily meagre exposition give rise to the mistaken notion that localizing an impression consists wholly and solely in performing or imaging the particular movements necessary to all active touches to a group of passive impressions. That this cannot suffice is evident merely from the consideration that a single position out of relation to all other positions is a contradiction. Localization, though it depends on many special experiences of the kind de--ribed, is not like an artificial product which is completed a part at a time, but is essentially a growth, its several constituent localizations advancing together in definiteness and interconnexion. So far has this development advanced that we do not even imagine the special movements which the lowalization of an impression implies, that is to say, they are no longer distinctly represented as they would be if we definitely intended to make them: the past experiences are “ retained," but too much blended in the mere perception to be appropriately spoken of as remembered or imaged. Apos of this almost instinctive character of even our curliot al perceptions it will be appropriate to animadvert on a mis. - : impliation in the current use of such terms as "localization." “ projection.” “b-lily reference.” “spatial reference," and this liko. Ti- implication is that external space, or the body as extended, is in -one sort presented or suppose-1 apart from the localization. rootion. or reference of impressions to such space. That it may - to ble to put a book in its place on a shelf there must to lo the book, and 2, distinct and apart from it, the place on the shelf.
material, is opposed to what is mental; as the existent or actual it is opposed to the non-existent; and again, what is actual is distinguished from what is possible or necessary. But here both terms, with a certain shade of difference, in so far as actual is more appropriate to movements and events, are used, in antithesis to whatever is ideal or represented, for what is sense-given or presented. This seems at least their primary psychological meaning; and it is the one most in vogue in English philosophy at any rate, over-tinged as that is with psychology." Any examination of this characteristic will be best deferred till we come to deal with ideation generally (see p. 5S below). Meanwhile it may suffice to remark that reality or actuality is not a single distinct element added to the others which enter into the complex presentation we call a thing, as colour or solidity may be. Neither is it a special relation among these elements, like that of substance and attribute, for example. In these respects the real and the ideal, the actual and the possible, are alike: all the elements or qualities within the complex, and all the relations of those elements to each other, are the same in the rose represented as in the presented rose. The difference turns not upon what these elements are, regard, d as qualities or relations presented or represented, but upon whatever it is that distinguishes the presentation from the representation of any given qualities or relations. Now this, as we shall see, turns partly upon the relation of such complex presentation to other presentations in consciousness with it, partly upon its relation as a presentation to the subject whose presentation it is. In this re-lot we find a difference, not only hotween the simple qualities, such as cold, hard, red, and sweet in strawberry ice, '..s., as presented and as represented, but also, though loss conspicuously, in the spatial, and even the temporal, r, lations which inter into our intuition as distinct from our in...sination of it. Where no such difference exists we have pass, d beyond
the distinction of percept and image to the higher level of conception and thought. So, then, reality or actuality is not strictly an item by itself, but a characteristic of all the items that follow. (b) Here our properly motor presentations or “feelings of effort or innervation ” come specially into play. They are not entirely absent in those movements of exploration by which we attain a knowledge of space; but it is when these movements are definitely resisted, or are only possible by increased effort, that we reach the full meaning of body as that which occupies space. Heat and cold, light and sound, the natural man regards as real, and by and by perhaps as due to the powers of things known or unknown, but not as themselves things. At the outset things are all corporeal like his own body, the first and archetypal thing, that is to say: things are intuited only when touch is accompanied by pressure; and, though at a later stage passive touch without pressure may suslice, this is only because pressures depending on a subjective initiative, i.e., on voluntary muscular exertion, have been previously experienced. It is of more than psychological interest to remark how the primordial factor in materiality is thus due to the projection of a subjectively determined reaction to that action of a not-self on which sense-impressions depend,an action of the not-self which, of course, is not known as such till this projection of the subjective reaction has taken place. Still we must remember that accompany
ness. The first step in this process has been the simultaneous projection into the same occupied space of the several impressions which we thus come to regard as the qualities of the body filling it. Yet such simultaneous and coincident projection would avail but little unless the constituent impressions were again and again repeated in like order so as to prompt anew the same grouping, and unless, further, this constancy in the one group was present along with changes in other groups and in the general field. There is nothing in its first experience to tell the infant that the song of the bird does not inhere in the hawthorn whence the notes proceed, but that the fragrance of the may-flower does. It is only where a group, as a whole, has been found to change its position relatively to other groups, and —apart from causal relations—to be independent of changes of position among them, that such complexes can become distinct unities and yield a world of things. Again, because things are so often a world within themselves, their several parts or members not only having distinguishing qualities but moving and changing with more or less independence of the rest, it comes about that what is from one point of view one thing becomes from another point of view several,—like a tree with its separable branches and fruits, for example. Wherein, then, more precisely, does the unity of a thing consist This question, so far as it here admits of answer, carries us over to temporal continuity.
ing sense-impressions are a condition of its projection : muscular effort without simultaneous sensations of contact
(d) Amidst all the change above described there is one Tempo. thing comparatively fixed : our own body is both constant ral con...tinuity.
would not yield the distinct presentation of the resistant occupying the space into which we have moved and would move again. Nay more, it is in the highest degree an essential circumstance in this experience that muscular effort, though subjectively initiated, is still only possible when there is contact with something that, as it seems, is making an effort the counterpart of our own. But this something is so far no more than thing-stuff; without the elements next to be considered our psychological individual would fall short of the complete intuition of distinct things.
as a group and a constant item in every field of groups; and not only so, but it is beyond all other things an object of constant and peculiar interest, inasmuch as our earliest pleasures and pains depend solely upon it and what affects it. The body becomes, in fact, the earliest form of self, the first datum for our later conceptions of permanence and individuality. A continuity like that of self is then transferred to other bodies which resemble our own, so far as our direct experience goes, in passing continuously from place to place and undergoing only partial and gradual changes of form and quality. As we have ex
Unity (c) The remaining important factors in the psychologi- isted—or, more exactly, as the body has been continuously o * cal constitution of things might be described in general | presented—during the interval between two encounters * terms as the time-relations of their components. Such with some other recognized body, so this is regarded as
relations are themselves in no way psychologically determined; impressions recur with a certain order or want of order quite independently of the subject's interest or of any psychological principles of synthesis or association whatever. It is CŞsential that impressions should recur, and recur as they have previously occurred, if knowledge is ever to begin ; out of a continual chaos of sensation, all matter and no form, such as some philosophers describe, nothing but chaos could result. But a flux of impressions having this real or sense-given order will not suffice; there must be also attention to and retention of the order, and these indispensable processes at least are psychological. Still they need not be further emphasized here, nor would it have been necessary at this point to call them to mind at all had not British empirical philosophers brought psychology into disrepute by overlooking them altogether. But for its familiarity we should marvel at the fact that out of the variety of impressions simultaneously presented we do not instantly group together all the sounds and all the colours, all the touches and all the smells, but, dividing what is given together, single out a certain sound or smell as belonging with a certain colour and feel, similarly singled out from the rest, to what we call one thing. We might wonder, too—those at least who have made so much of association by similarity ought to wonder—that, say, the white of snow calls up directly, not other shades of white or other colours, but the expectation of cold or of powdery soft
having continuously existed during its absence from us. IIowever permanent we suppose the conscious subject to be, it is hard to see how, without the continuous presentation to it of such a group as the bodily self, we should ever be prompted to resolve the discontinuous presentations of external things into a continuity of existence. It might be said: “Since the second presentation of a particular group would, by the mere workings of psychical laws, coalesce or become identical with the image of the first, this coalescence suffices to “generate’ the conception of continued existence.” But such assimilation is only the ground of an intellectual identification and furnishes no motive, one way or the other, for resolving two like things into the same thing : between a second presentation of A and the presentation at different times of two A's there is so far no difference. Real identity no more involves exact similarity than exact similarity involves sameness of things; on the contrary, we are wont to find the same thing alter with time, so that exact similarity after an interval, so far from suggesting one thing, is often the surest proof that there are two concerned. Of such real identity, then, it would seem we must have direct experience; and we have it in the continuous presentation of the bodily self; apart from this it could not be “generated" by association among changing presentations. Other bodies being in the first instance personified, that then is regarded as one thing—from whatever point of view we look at it, whether
as part of a larger thing or as itself compounded of such parts—which has had one beginning in time. But what is it that has thus a beginning and continues indefinitely? This leads to our last point. (e) So far we have been concerned only with the combination of sensory and motor presentations into groups and with the differentiation of group from group; the relations to each other of the constituents of each group still for the most part remain. To these relations in the main must be referred the correlative conceptions of substance and attribute, the distinction in substances of qualities and powers, of primary qualities and secondary, and the like." Of all the constituents of things only one is universally present, that above described as physical solidity, which presents itself according to circumstances as impenetrability, resistance, or weight. Things differing in temperature, colour, taste, and smell agree in resisting compression, in filling space. Because of this quality we regard the wind as a thing, though it has neither shape nor colour, while a shadow, though it has both but not resistance, is the very type of nothingness. This constituent is invariable, while other qualities are either absent or change,_form altering, colour disappearing with light, sound and smells intermitting. Many of the other qualities—colour, temPerature, sound, smell—increase in intensity until we reach and touch a body occupying space; with the same movement too its visual magnitude varies. At the moment of contact an unvarying tactual magnitude is ascertained, while the other qualities and the visual magnitude reach a fixed maximum ; then first it becomes possible by effort to change or attempt to change the position and form of what we apprehend. This tangible plenum we thenceforth regard as the seat and source of all the qualities we project into it. In other words, that which occupies space is psychologically the substantial; the other real constituents are but its properties or attributes, the marks or manifestations which lead us to expect its presence. Imagination or Ideation. Before the intuition of things has reached a stage so complete and definite as that just described, imagination or ideation as distinct from perception has well begun. In passing to the consideration of this higher form of mental life we have to note the distinction between impressions and images or ideas, to which Hume first gave general currency. Hume did not think it “necessary to employ many words in explaining this distinction. Every one of himself will readily perceive the difference . . . ; though it is not impossible but in particular instances they may very nearly approach to each other. Thus in sleep, in a fever, in madness, or in any very violent emotions of soul, our ideas may approach to our impressions; as, on the other hand, it sometimes happens our impressions are so faint and low that we cannot distinguish them from our ideas once in intensity, or, as Hume puts it, “in the force or liveliness with which they strike upon the mind," is a sufficient characteristic, but we must examine a good deal further and lay more attention to his uncertain cases if this important distinction is ever to be in any sense I-yehologically “explained." To losin with, it is very questionable whether Hume was right in applying Locke's distinction of simple and “mplex to ideas in the narrower sense as well as to in
In most cases, no doubt, the obvious differ
Characteristics of ideas.
plexes as a preliminary to new combinations. But it is doubtful whether the results of such an analysis are ever the ultimate elements of the percept, that is, merely isolated impressions in a fainter form. We may now try to ascertain further the characteristic marks which distinguish what is imaged from what is perceived. The most obvious, if not the most invariable, difference is that which, as we have seen, Hume calls the superior force or liveliness of primary presentations as compared with secondary presentations. But what exactly are we to understand by this somewhat figurative language? A simple difference of intensity cannot be all that is meant, for, though we may be momentarily confused, we can perfectly well distinguish the faintest impression from an image, and yet can hardly suppose the faintest impression to be intenser than the most lively image. Moreover, we can reproduce such faintest impressions in idea, so that, if everything depended on intensity, we should be committed to the gratuitous supposition that secondary presentations can secure attention with a less intensity than is required for primary presentations. The whole subject of the intensity of representations awaits investigation. Between moonlight and sunlight or between midday and dawn we could discriminate many grades of intensity; but it does not appear that there is any corresponding variation of intensity between them when they are not seen but imagined. Many persons suppose they can imagine a waxing or a waning sound or the gradual abatement of an intense pain; but what really happens in such cases is probably not a rise and fall in the intensity of a single representation, but a change in the complex represented. In the primary presentation there has been a change of quality along with change of intensity, and not only so, but most frequently a change in the muscular adaptations of the sense-organs too, to say nothing of organic sensations accompanying these changes. A representation of some or all of these attendants is perhaps what takes place when variations of intensity are supposed to be reproduced. Again, hallucinations are often described as abnormally intense images which simply, by reason of their intensity, are mistaken for percepts. But such statement, though supported by very high authority, is almost certainly false, and would probably never have been made if physiological and epistemological considerations had been excluded as they ought to have been. Hallucinations, when carefully examined, seem just as much as percepts to contain among their constituents some primary presentation—either a socalled subjective sensation of sight and hearing or some organic sensation due to deranged circulation or secretion. Now we have noticed already incidentally in a preceding paragraph that primary presentations reinstate and maintain the representational constituents of a percept in a manner very different from that in which what are unmistakably ideas reproduce each other. The intensity and steadiness of the impressional elements are, as it were, shared by the ideational elements in a complex containing both. Intensity alone, then, will not suffice to discriminate, neither will extremes of intensity alone lead us to confuse, impressions and images. The superior steadiness just mentioned is perhaps a more constant and not less striking characteristic of percepts. Ideas are not only in a continual flux, but even when we attempt forcibly to detain one it varies continually in clearness and completeness, reminding one of nothing so much as of the illuminated devices made of gas jets, common at fêtes, when the wind sweeps across them, momentarily obliterating one part and at the same time intensifying another. There is not this perpetual flow and flicker in what we perceive ; for this, unlike the train of ideas, has at the outset neither a logical nor a
psychological continuity. The impressions entering consciousness at any one moment are psychologically independent of each other; they are equally independent of the impressions and images presented the moment before —independent, i.e., as regards their order and character, not, of course, as regards the share of attention they secure. Attention to be concentrated in one direction must be withdrawn from another, and images may absorb it to the exclusion of impressions as readily as a first impression to the exclusion of a second. But, when attention is secured, a faint impression has a fixity and definiteness lacking in the case of even vivid ideas. One ground for this definiteness and independence lies in the localization or projection which accompanies all perception. But why, if so, it might be asked, do we not confound percept and image when what we imagine is imagined as definitely localized and projected" Because we have a contrary percept to give the image the lie; where this fails, as in dreams, or where, as in hallucination, the image obtains in other ways the fixity characteristic of impressions, such confusion does in fact result. But in normal waking life we have the whole presentation-continuum, as it were, occupied and in operation: we are distinctly conscious of being embodied and having our senses about us. This contrariety between impression and image suggests, however, a deeper question: we may ask, not how it is resolved, but how it is possible. With eyes wide open, and while clearly aware of the actual field of sight and its filling, one can recall or imagine a wholly different scene: lying warm in bed one can imagine oneself out walking in the cold. It is useless to say the terms are different, that what is perceived is present and what is imaged is past or future." The images, it is true, have certain temporal marks—of which more presently—by which they may be referred to past or future; but as imaged they are present, and, as we have just observed, are regarded as both actual and present in the absence of correcting impressions. We cannot at once see the sky red and blue; how is it we can imagine it the one while perceiving it to be the other? When we attempt to make the field of sight at once red and blue, as in looking through red glass with one eye and through blue glass with the other, either the colours merge and we see a purple sky or we see the sky first of the one colour and then of the other in irregular alternation. That this does not happen between impression and image shows that, whatever their connexion, images altogether are distinct from the presentation-continuum and cannot with strict propriety be spoken of as revived or reproduced impressions. This difference is manifest in another respect, viz., when we compare the effects of diffusion in the two cases. An increase in the intensity of a sensation of touch entails an increase in the extensity; an increase of muscular innervation entails irradiation to adjacent muscles; but when a particular idea becomes clearer and more distinct there rises into consciousness an associated idea qualitatively related probably to impressions of quite another class, as when the smell of tar calls up memories of the sea-beach and fishing-boats. Since images are thus distinct from impressions, and yet so far continuous with each other as to form a train in itself unbroken, we should be justified, if it were convenient, in speaking of images as changes in a representation- or memory-continuum ; and later on we may see that this is convenient. Impressions, then, have no associates to whose presence their own is accommodated and on whose intensity their own depends. Each bids independently for attention, so
* Moreover, as we shall see, the distinction between present and past or future psychologically presupposes the contrast of impression and image.