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Local

signs.

tion, 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 pre-
sentation 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.,
in 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.

impatience, that this amounts to the monstrous absurdity | hardly perhaps implied in the mere massiveness of a sensa-
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 inten-
sity 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. Inten-
sity 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 presentation-
continuum 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 pre-
sentation becoming nil, such presentation has two or
more local signs, its parts, taken separately, though
identical in quality and intensity, having a different rela-
tion 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 pos-
sibility 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.1
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 coin-
cident and the next widely separate.2 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.

1 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

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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.

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2 The improvements in the sensibility of our spatial sense consequent on its variations under practice, the action of drugs, &c., are

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, PPPP4 P1 cannot be presented along with P2, and from P it is impossible to reach P1 again save through P3 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.

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the body-probably our earliest lesson in spatial perception | But in the evolution of our spatial experience impressions and -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 la and 1, 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 7 and 1, on the hand or arm, and we place a finger upon and move it to l,, experiencing thereby the series P1, P2P3,P4, this series constitutes la 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 Fb Fc Fd F. F, F, Fr Fr Tttt P1PaPa Ps

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1

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 sensations of the continuum as a whole; T stands for the active touch of the exploring finger and P1 for the corresponding 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 ttt and P2P3P4 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 localized 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 add 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 described, 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 localization 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.

Apropos of this almost instinctive character of even our earliest spatial perceptions it will be appropriate to animadvert on a misleading implication in the current use of such terms as "localization," projection," "bodily reference," "spatial reference," and the like. The implication is that external space, or the body as extended, is in some sort presented or supposed apart from the localization, projection, or reference of impressions to such space. That it may be possible to put a book in its place on a shelf there must be (1) the book, and (2), distinct and apart from it, the place on the shelf.

positions are not thus presented apart. We can have, or at least localized; but if it is localized this means that a more complex we can suppose, an impression which is recognized without being 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 impression 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.

1

(a) The terms actuality and reality have each more Actualthan one meaning. Thus what is real, in the sense of ity or reality. 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. 58 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 repreThe difference turns not sented as in the presented rose. upon what these elements are, regarded 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 respect we find a difference, not only between the simple qualities, such as cold, hard, red, and sweet in strawberry ice, e.g., as presented and as represented, but also, though less conspicuously, in the spatial, and even the temporal, relations which enter into our intuition as distinct from our imagination of it. Where no such difference exists we have passed beyond

1 Thus Locke says, "Our simple ideas [i.e., presentations or impressions, as we should now say] are all real and not fictions at pleasure; for the mind can make to itself no simple idea more than what it has received" (Essay, ii. 30, 2). And Berkeley says, "The ideas imprinted on the senses by the Author of Nature are called real things; and those excited in the imagination, being less regular, vivid, and constant, are more properly termed ideas or images of things, which they copy or represent" (Prin. of Hum, Know., part i. § 33).

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.

Impene- (6) Here our properly motor presentations or "feelings
trability. 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 pos-
sible 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 pass-
ive touch without pressure may suffice, this is only because
pressures depending on a subjective initiative, i.e., on
voluntary muscular exertion, have been previously experi-
enced. 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-
ing sense-impressions are a condition of its projection:
muscular effort without simultaneous sensations of contact
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 in-
dividual would fall short of the complete intuition of dis-
tinct things.

Unity

ness. The first step in this process has been the simultane-
ous 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 im-
pressions 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, be-
cause 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 inde-
pendence 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.

tinuity.

(d) Amidst all the change above described there is one Tempothing comparatively fixed: our own body is both constant ral conas 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 existed-or, more exactly, as the body has been continuously presented during the interval between two encounters with some other recognized body, so this is regarded as having continuously existed during its absence from us. However 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 But for its familiarity we should marvel at the fact that exact similarity than exact similarity involves sameness of out of the variety of impressions simultaneously presented things; on the contrary, we are wont to find the same thing we do not instantly group together all the sounds and all alter with time, so that exact similarity after an interval, so the colours, all the touches and all the smells, but, divid- far from suggesting one thing, is often the surest proof that ing what is given together, single out a certain sound or there are two concerned. Of such real identity, then, it smell as belonging with a certain colour and feel, similarly would seem we must have direct experience; and we have singled out from the rest, to what we call one thing. We it in the continuous presentation of the bodily self; apart might wonder, too-those at least who have made so much from this it could not be " generated" by association of association by similarity ought to wonder-that, say, the among changing presentations. Other bodies being in white of snow calls up directly, not other shades of white or the first instance personified, that then is regarded as one other colours, but the expectation of cold or of powdery soft-thing-from whatever point of view we look at it, whether

(c) The remaining important factors in the psychologiand com- cal constitution of things might be described in general plexity. terms as the time-relations of their components. Such 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 essential 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.

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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.

Substan. (e) So far we have been concerned only with the comtiality. bination 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.1

Impres

sions

and

ideas,

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.

pressions. "That idea of red," says Hume, "which we | form in the dark and that impression which strikes our eyes in the sunshine differ only in degree, not in nature."3 But what he seems to overlook is that, whereas there can be a mere sensation red-and such a presentation may for present purposes be regarded as simple we can only have an image or representation of a red thing or a red form, i.e., of red in some way ideally projected or intuited. In other words, there are no ideas answering to simple or isolated impressions: what are revived in memory and imagination are percepts, not unlocalized sensations and movements. It is not only that we cannot now directly observe such representations,—because, for that matter, we can no longer directly observe even the original presentations as merely elementary impressions; the point rather is that ideas as such are from the first complex, and do not begin to appear in consciousness apart from the impressions which they are said to reproduce till after these impressions have been frequently attended to together, and have been more or less firmly synthesized into percepts or intuitions.

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The effects of even the earliest of these syntheses or "associations' of impressions must of course in some way persist, or progress in perception would be impossible. On this account it has been usual to say that "perception" implies both "memory" and "imagination"; but such a statement can be allowed only so long as these terms are vaguely used. The dog's mouth waters only at the sight of food, but the gourmand's mouth will also water at the thought of it. We recognize the smell of violets as certainly as we recognize the colour when the spring brings them round again; but few persons, if any, can recall the scent when the flower has gone, so as to say with Shelley

"Odours, when sweet violets sicken,
Live within the sense they quicken "-

though most can recall the colour with tolerable clearness. In like manner everybody can perform innumerable complex voluntary movements which only a few can mentally rehearse or describe without the prompting of actual execution. And not only does such reproduction as suffices for perception fall short of that involved in reminiscence or memory in the narrower sense, but the manner in which the constituent elements in a perception are combined differs materially from what is strictly to be called the association of ideas. To realize this difference we need only to observe first how the sight of a suit of polished armour, for example, Before the intuition of things has reached a stage so instantly reinstates and steadily maintains all that we retain of complete and definite as that just described, imagination former sensations of its hardness and smoothness and coldness, or ideation as distinct from perception has well begun. and then to observe how this same sight gradually calls up ideas In passing to the consideration of this higher form of now of tournaments, now of crusades, and so through all the changing imagery of romance. Though the percept is complex, mental life we have to note the distinction between im- it is but a single whole, and the act of perception is single too; pressions and images or ideas, to which Hume first gave but, where, as is the case in memory and imagination, attention general currency. Hume did not think it "necessary to passes, whether voluntarily or non-voluntarily, from one representation to another, it is obvious that these several objects of employ many words in explaining this distinction. Every attention are still distinct and that it is directed in turn to each. one of himself will readily perceive the difference ..; The term "association seems only appropriate to the latter: To though it is not impossible but in particular instances the connexion of the partial presentations in a complex, whether they may very nearly approach to each other. Thus in perception or idea, it would be better to apply the term "complication," which was used in this sense by Herbart, and has been so sleep, in a fever, in madness, or in any very violent emotions used by many psychologists since. When we perceive an orange of soul, our ideas may approach to our impressions; as, by sight we may say that its taste or feel is represented, when we on the other hand, it sometimes happens our impressions perceive it by touch we may in like manner say that its colour is are so faint and low that we cannot distinguish them from represented, symbolizing the whole complex in the first case our ideas." In most cases, no doubt, the obvious differ- sufficiently for our present purpose as Ctf, in the second as Fct. We might also symbolize the idea of an orange as seen by c' tf and ence in intensity, or, as Hume puts it, "in the force or the idea of an orange as felt by f'ct, using the accented letter to liveliness with which they strike upon the mind," is a signify that different constituents are dominant in the two cases. sufficient characteristic, but we must examine a good deal What we have, then, to observe is briefly (1) that the processes further and pay more attention to his uncertain cases if by which the whole complex c'tf or fet is brought into consciousness differ importantly from the process by which C or Freinthis important distinction is ever to be in any sense states and maintains tf or c t, and (2) that e, f, and never have psychologically "explained." that distinct existence as representations which they had as presentations or impressions.

To begin with, it is very questionable whether Hume was right in applying Locke's distinction of simple and complex to ideas in the narrower sense as well as to im

The distinction between the thing and its properties, like all the foregoing distinctions, is one that might be more fully treated under the head of "Thought and Conception." Still, inasmuch as the material warrant for these concepts is contained more or less implicitly in our percepts, some consideration of it is in place here.

Treatise of Human Nature, book i. part i. § 1.

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The mental synthesis which has taken place in the evolu tion of the percept can only partially fail in the idea, and never so far as to leave us with a chaotic "manifold" of mere sensational remnants. On the contrary, we find that in "constructive imagination" a new kind of effort is often requisite in order to dissociate these representational com

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plexes as a preliminary to new combinations. But it is | psychological continuity. The impressions entering con-
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
teristics is that which, as we have seen, Hume calls the superior
of ideas. 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 per-
fectly 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 in-
tensity 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 ima-
gined. 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 representa-
tion, 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 so-
called subjective sensation of sight and hearing or some
organic sensation due to deranged circulation or secretion.
Now we have noticed already incidentally in a preced-
ing paragraph that primary presentations reinstate and
maintain the representational constituents of a percept in a
manner very different from that in which what are unmis-
takably 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 discrimi-
nate, 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

sciousness at any one moment are psychologically inde-
pendent 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 definite-
ness and independence lies in the localization or projec-
tion 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 con-
fusion does in fact result. But in normal waking life we
have the whole presentation-continuum, as it were, occu-
pied 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.1 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 im-
pressions. 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 impres-
sion and image shows that, whatever their connexion,
images altogether are distinct from the presentation-con-
tinuum 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 prob-
ably to impressions of quite another class, as when the
smell of tar calls up memories of the sea-beach and fish-
ing-boats. Since images are thus distinct from impres-
sions, 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 repre-
sentation- 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

1 Moreover, as we shall see, the distinction between present and past or future psychologically presupposes the contrast of impression and image.

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