ness. Since it is the subject, not the object that is conscious, the term state of consciousness implies strictly a subjective reference; subjective modifications, either affective or active. The former and so it is only applicable to sensations, if they are regarded as would identify sensation with feeling, and this for reasons already given-we must disallow. But it is true that a sensation, like other presentations, implies the subjective activity we call attention; it of it. This relation is expressed in German by means of the distincis not, however, a modification or state of this activity, but the object tion generally of Vorstellen and Vorstellung and in the present case of Empfinden and Empfindung; and German psychology has gained in clearness in consequence. The distinction of conception and concept (conceit) is to be found in older English writers and was revived by Sir W. Hamilton, who suggested also the analogous distinction of perception and percept. It would be a great gain if there were a corresponding pair of terms to distinguish between driven to say. Reception and recept at once occur and seem unex"the sensing act and the object "sensed," as some have been ceptionable apart, of course, from their novelty. At any rate, if we are to rest content with our present untechnical terminology we must understand sensations to mean objective changes as they first break in upon the experience of our psychological individual; in this respect Locke's term " impression" has a certain appropriateness. What we ordinarily call a single sensation has not only a characteristic quality but it is also quantitatively determined in respect of intensity, protensity (or duration) and extensity. A plurality of properties, it may be said, straightway implies complexity of some sort. This is obvious and un- Character deniable; psychological-as distinct from psychical istics of analysis of simple sensations is possible, and the Sensation. description just given is reached by means of it. Such analysis, however, presupposes the comparison of many sensations; but to the complexity it discloses there is no answering plurality discernible in the immediate experience of a single sensation. To make this clearer let us start from a case in which such plurality can be directly verified. In a handful of rose petals we are aware at once of a definite colour, a definite odour and a definite "feel." Here there is a plurality (a+b+c), any part of which can be withdrawn from our immediate experience without prejudice to the rest, for we can close the eyes, hold the nose, or drop the petals on the table. Let us now turn to the colour alone; this we say has a certain quality, intensity, extensity, &c. But not only have we not one sense for quality, another for intensity, &c., but we cannot reduce the intensity to zero and yet have the quality remaining; nor can we suppress the quality and still retain the extensity. In this case then what we have is not a plurality of presentations (a+b +c), but a single presentation having a plurality of attributes (a b c) so related that the absence of any one annihilates the whole. But though, as already said, such single presentation gives, as it stands, no evidence of this plurality, yet it is to be remembered that in actual experience we do not deal with sensations in isolation; here, accordingly, we find evidence in plenty to justify our psychological analysis. In innumerable cases we experience varieties of intensity with little or no apparent change of quality, as happens, for example, when a sounding pitch-pipe is moved towards or away from the ear; and continuous changes of quality without any change of intensity, as happens when the pipe is shortened or lengthened without any alteration of position. We may have tactual or visual sensations which vary greatly in extensity without any striking change of quality, and we may have such sensations in every possible variety of quality without any changes of extensity.

or what the more careful of them call irritability; and, true again, that this irritability is invariably preceded by a physical process called stimulation. But it may be urged, why not recognize a connexion that actually obtains, since otherwise sensation must remain unexplained? Well, in the first place, such "psychophysical" connexion is not a psychological explanation: it cannot be turned directly to account in psychology, either analytic or genetic. Next the psychological fact called sensation always is, and at bottom always must be, independently ascertained; for the physiological or irritation has not necessarily a concomitant neurosis "psychosis or sensation and, strictly dealt with, affords no hint of such. Finally, this inexplicability of sensation is a psychological fact of the utmost moment: it answers to what we call reality in the primary sense of the term. The psychophysicist, in setting out to explain sensation, has-unawares to himself-left this fundamental reality behind him. For it belongs essentially to individual experience, and this-in assuming the physical standpoint-he has of course transcended. Nevertheless the mistake of method that here reveals itself was perhaps inevitable, for the facts of another's sense-organs and their physical excitants must have obtruded themselves on observation long before the reflective attitude was advanced enough to make strictly psychological analysis possible. The psychophysical standpoint, that is to say, was attained before the purely psychological; and the consequent bias is only now in process of correction. A series of physical processes, first without and then within the organism-ethereal or aërial vibrations, neural and cerebral excitations-was the starting point. What comes first, immediately, and alone, in the individual's experience, and is there simply and positively real, was then misinterpreted as subjective modification, mental impression, species sensibiles, or the like. For from the days of Democritus to our own the same crude metaphor has prevailed without essential variation. And here the saying holds: Vestigia nulla retrorsum. Into the man's head the whole world goes, including the head itself Such thoroughgoing "introjection" affords no ground for subsequent "projection." Thus the endeavour to explain sensation overreaches itself: the external object or thing that was supposed to cause sensations and to be therefore distinct from them, was in the end wholly resolved into these and regarded as built out of them by association (Mill) or by apperceptive synthesis (Kant). But no "mental chemistry," no initial alchemy of " 'forms," can generate objective reality from feelings or sense-impressions as psychophysically defined.1 A's experience as it is for B is not real but inferential; and if the grounds of the inference, which are the only realities for B, are to be regarded as the causes of which A's experiences are merely the effects, then the two experiences are on a wholly different footing. When A treats B in the same fashion we get the world in duplicate: (1) as original and outside, i.e. as cause, and (2) as copied within each percipient's head, i.e. as effect. But when B interprets his own experience as he had interpreted A's we seem to have lost the real world altogether. In presence of this dilemma, the philosophers of our time, as already said, are feeling it needful to revise their psychology. The question of method is vital. If the psychophysical standpoint were the more fundamental, psychology would be based on physiology, and the old definition of sensation might stand. If, on the other hand, is the exclusive business of psychology to analyse and trace the development The numerous and striking diversities among our present of individual experience as it is for the experiencing individual, sensations are obviously not primordial; what account then then-however much neurological evidence may be employed can we give of their gradual differentiation? Some psychoas a means of ascertaining psychological facts-the facts them-logists have assumed the existence of absolute "units of selves must be scrupulously divested of all physical implications, the psychophysical method takes a secondary place, and the objective reality of "sensory" presentations stands unimpeached.

Latin recipere; it expresses only the comparative passivity of sense. Reception does not in English suggest the taking back of the In contrast to percipere (to take entire possession of) it implies the absence of that assimilation which is essential to perception; and finally it contrasts appropriately with retention.

tant.

This distinction, though continually overlooked, is vitally impor By psychological analysis we mean such analysis as the psychological observer can reflectively make, by psychical analysis only such analysis as is possible in the immediate experience of the subject observed.

2a

ence of quality, is probably due to the fact that several nerveterminations are excited in each case: where the sensation is one of smoothness all are stimulated equally; where it is one of roughness the ridges compress the nerve-ends more, and the hollows compress them less, than the level parts do. The most striking instance in point, however, is furnished by the differences in musical sounds, to which the name timbre is given. To the inattentive or uninstructed ear notes or “ compound tones" appear to be only qualitatively diverse and not to be complexes of simple tones. Yet it is possible with attention and practice to distinguish these partial tones in a note produced on one instrument, a horn, say, and to recognize that they are different from those of the same note produced on a different instrument, for example, a violin.

sensibility," all identically the same, and explain the unlike- | unpolished, though to direct introspection an irresolvable differnesses in our existing sensations as resulting "from unlike Differentia modes of integration of these absolute units." tion of The sole evidence on which they rely is physiological, Sensation. the supposed existence of a single nerve shock or neural tremor. It is true that in an extirpated nerve what is known as the "negative variation" is approximately such an isolated event of uniform quality. But the same cannot be said of what happens during the stimulation of a nerve in situ with its peripheral and central connexions still intact. The only evidence apparently to which we can safely appeal in this inquiry is that furnished by biology. Protoplasm, the socalled "physical basis of life," is amenable to stimulation by every form of physical agency-mechanical, chemical, thermal, photical, electrical-with the single exception of magnetism; and in keeping with this it is found that unicellular organisms respond, and respond in ways more or less peculiar, to each of these possible modes of excitation. Since, so far as is known, there is no morphological separation of function in these lowest forms of life, it is reasonably assumed that the single cell acts the part of universal sense-organ," and that the advance to such complete differentiation of sense-organs as we find among the higher vertebrates has been a gradual advance. Numerous facts can now be adduced of the occurrence of "transitional " or "alternating" sense-organs among the lower forms of multicellular animals; organs, that is to say, which are normally responsive to two or more kinds of stimulus, and thus hold an intermediate position between the universal sense-organ of the Protozoa and the special sense-organ of the Mammalia. For example, a group of cells which would behave towards all stimuli impartially were they independent unicellular organisms become, as an organ in a multicellular organism, amenable only to mechanical or only to chemical stimuli,-become, that is to say, an organ of touch and of hearing, or an organ of taste and also of smell; until, finally, when differentiation is sufficiently advanced, the group ends by becoming exclusively the organ of one specified sense, touch or hearing in the one case, taste or smell in the other. Of course the imperfectly specialized sensations, say of the leech, and still more the wholly unspecialized sensations of the amoeba, cannot be regarded as blends of some or all of those which we are said to receive through our five senses. We must rather suppose that sensations at the outset corresponded very closely with the general vital action of stimuli as distinct from their action on specially differentiated sensory apparatus. Even now we are still aware of the general effects of light, heat, fresh air, food, &c., as invigorating or depressing quite apart from their specific qualities. Hence the frequent use of the term general or common sensibility (coenesthesis). But, though less definitely discriminated, the earlier, and what we call the lower, sensations are not any less concrete than the later and higher. They have been called general rather than specific, not because psychologically they lack any essential characteristic of sensation which those acquired later possess, but simply because physiologically they are not, like these, correlated to special sense-organs.

of

But, short of resolving such sensations into combinations of one primordial modification of consciousness, if we could Complexity conceive such, there are many interesting facts which point clearly to a complexity that we can Sensations. seldom directly detect. Several of our supposed sensations of taste, e.g., are complicated with sensations of touch and smell: thus the pungency of pepper and the dryness of wine are tactual sensations, and their spicy flavours are really smells. How largely smells mingle with what we ordinarily take to be simply tastes is best brought home to us by a severe cold in the head, as this temporarily prevents the access of exhalations to the olfactory surfaces. The difference between the smooth feel of a polished surface and the roughness of one that is

Cf. G. H. Lewes, Problems of Life and Mind (1879), vol. iii. pp. 250 sqq.; H. Spencer, Principles of Psychology, vol. i. § 60.

Cf. W. A. Nagel," Die Phylogenese specifischer Sinnesorgane," Bibliotheca zoologica (1894), pp. 1-42.

In like manner many persons believe that they can discriminate in certain colours, hence called "mixed," the elementary colours of which they are held to be composed; red and yellow, for example, in orange, or blue and red in violet. But in so thinking they appear to be misled, partly by the resemblance that certainly exists between orange and red, on the one hand, and orange and yellow on the other, the two colours between which in the colour spectrum it invariably obtainable by the mixture of red and yellow pigments; and so in the stands; and partly by the knowledge that, as a pigment, orange is other cases. As we shall see later, however (§ 39), in this particular case of sensory continua, resemblance is no proof of complexity. Were it otherwise we should have to conclude that a given tone, ought to be a blend of both; whereas, in point of fact, the tone dsince this also resembles the two between which it is intermediate, though as regards pitch it has a certain resemblance to c and e, its neighbours on either side-differs widely from the chord c-e, which is made up of these. In all cases in which the psychical complexity of a sensation is beyond dispute the partial sensations are distinsity as well. Thus, if the skin be touched by the point of a hot or guished by discernible differences of extensity, and usually of intencold bradawl the temperature sensation has not the punctual character of the touch but seems rather to surround this as a sort of penumbra. Similarly, the ground-tone of a clang-complex has not over-tones. There is also in such cases a certain rivalry or antago only a greater intensity but also a greater extensity than any of the nism between the complex as an unanalysed whole and the complex as analysed, and even between the several partial sensations after such analysis. In the absence of such direct evidence it is unwarrantstimuli, even when this is really present. In the case of pigment able to infer psychical complexity from complexity in the physical mixture, however, there is no such physical complexity as is vulgarly supposed. And it is worth noting that white light is physically the most complex of all, whereas the answering sensation is not only simple but probably the most primitive of all visual sensations.

Every sensation within the fields of consciousness has sensibly some continuous duration and seems sensibly to admit of some continuous variation in intensity and exQuantitative tensity. But whether this quantitative continuity Continuity. of presentational change is more than apparent has been questioned. Sensations of almost liminal intensity are found to fluctuate every few seconds, and, as already remarked, when the threshold of intensity is actually reached, they seem intermittently to appear and disappear, a fact which Hume long ago did not fail to notice. The results of numerous experiments, however, justify the conclusion that these variations are due primarily to oscillation of attention, and furnish so far no ground for the assumption that even the liminal sensation is discontinuous. But again we can only detect a difference of intensity when this is of finite amount and bears a certain constant ratio to the initial intensity with which it is compared a fact commonly known as Weber's Law. But this imperfection in our power of discrimination is no proof that our sensations vary discontinuously; and not only is there no positive evidence in favour of such discontinuity, but it is altogether improbable on general grounds. Lastly, there is always more or less distinctness in the several nerve-endings as well as isolation of the nerve-fibres themselves. The skin, for example, when carefully explored, turns out to be a complex mosaic of so-called " spots," severally responding to stimulation by sensations of pressure, heat, cold and pain. But from this to argue that the extensity of a sensation is really a mere aggregate without any continuity is on a par with calling a lake a Cf. Stumpf, Tonpsychologie, ii. 58 seq.

collection of pools because it is fed by separate streams. If it could be shown that in the brain as a whole there is no functional continuity a formidable psychophysical problem would no doubt arise.

As regards the quality of sensations-the primitive sensation of sight appears to consist only of the single quality we call "light," a quality which ranges in intensity from Quality of a dazzling brightness that becomes painful and Sensations. blinding down to a zero of complete darkness; a limit which, however, is never completely attained, since the retina is always more or less internally stimulated-hence what is called the eye's own light (Eigenlicht). The first responses to light-stimulation seem to be very much on a par with our own to diffused heat or cold; some organisms seek the light and others shun it. As little as our temperature-sense yields us a perception of form does the light-sense at this level yield any Not until the stage of visual spatial perception is reached and some discrimination of form is possible, do black and white attain the meaning they now have for us. An object can be visually perceived only when its colour or shade differs from that of the surrounding field; so far black as a "secondary quality" is on a par with colour, that is to say, when we are talking of things it may be called a quality. But there is still an important difference; in a light field many colours or shades may be distinguished, but in a dark field none. Though it is correct to speak of perceiving a black object, must we not then maintain that-so far as it is really black the object yields us directly no sensation? Similarly, the piper is said to "feel" the holes in his whistle when actually he only touches the solid metal in which they are pierced; or the soldier is said to hear the tattoo, though he has no auditory sensation of the silence intervening between successive taps on the drum. And it has yet to be shown that there is any more justification for speaking of visual sensations without luminosity. Meanwhile we must maintain that in absolute darkness we do not see black, since we do not see at all. No doubt we are prone to identify the two concepts darkness and blackness, for what we may call their sensory content is the same, viz. the absence of visual sensation.

"

| limit, the so-called deep or grave tones become less "
even," till
at length distinct, more or less pervasive, tremors are felt rather
than heard as distinct impulses on the ear-drum. The so-called
high or acute tones again, as we approach their limit, are
accompanied by tactual, often more or less painful, sensations,
as if the ear were pierced by a fine needle. This connexion of
auditory with tactual sensations confirms the independent
evidence of biology pointing to an original differentiation of
sound from touch. The special characteristics of tone-com-
plexes, whether clangs or noises, are due to the remarkable
analytic power which belongs to the sense of hearing. Two
colours cannot be simultaneously presented unless they are
differently localized, but several tones may form one complex
whole within which they, as "partial" tones, are distinguish-
able, though spatially undifferentiated.

Unlike the higher senses of sight and hearing, the lower senses of touch, taste, smell, &c., do not constitute qualitative continua. Temperatures may indeed be represented as ranging in opposite directions, i.e. through heat or through cold, between a zero of no sensation and the organic sensations due to the destructive action of both extremes, heat and cold alike. But the continuity in this case is intensive rather than qualitative. Tastes fall into the four isolated qualities known as sweet, sour, bitter, saline; but smells hardly admit of classification at all. Sensations of touch and sight have in a pre-eminent degree a certain peculiar continuity which differentiations of extensity entail, and which we shall have presently to consider further under the title of local signs. The various sensations classed together as organic, hunger, thirst, physical pain, &c., are left to the physiologist to describe.

Our motor presentations contrast with the sensory by their want of striking qualitative differences. They are divided into two groups: (a) motor presentations proper and Movements. (b) auxilio-motor of kinaesthetic presentations. The former answer to our " feelings of muscular effort " or feelings of innervation." The latter are those presentations due to the straining of tendons, stretching and flexing of the skin, and the like, by which the healthy man knows that his efforts to move are followed by movement, and so knows the position of his body and limbs. It is owing to the absence of these presentations that the anaesthetic patient cannot directly tell whether his efforts are effectual or not, nor in what position his limbs have been placed by movements from without. Thus under normal circumstances motor presentations are always accompanied by auxilio-motor; but in disease and in passive movements they are separated and their distinctness thus made manifest. Originally we may suppose kinaesthetic presentations to have formed one imperfectly differentiated continuum, but now, as with sensations, they have become a collection of special continua, viz. the groups of movements possible to each limb and certain combinations of these movements.

Whereas in nature the only diffused light we need consider is that emitted by the sun, the rays transmitted by the things about us vary in physical quality and in their effects upon protoplasm. As soon, therefore, as visual forms can be distinguished, a differentiation among light-sensations becomes obviously advantageous. The first colours to be differentiated were probably yellow and blue, or perhaps it would be truer to say warm" colour and "cold" colour, upon which there followed a further differentiation of the warm colour into red and green. It is interesting to note that all possible sensations of colour constitute a specific continuum. We may represent it by a sphere, in which (a) the maximum of luminosity is at one pole and the minimum at the other; (b) the series of colours proper (red to violet and through purple back to red), constituting a closed line, are located round the equator or in zones parallel to it, according to shade; and (c) the amount of saturation (or absence of white) for any given zone of illumination increases with distance from the axis. In dealing with the quality of auditory sensations we have to But whereas kinaesthetic presentations were commonly allowed distinguish between the simple sensations called tones and the to be purely sensory, the concomitants of centripetal excitationshence the older name of "muscular or sixth sense" applied to them sensation-complexes, either clangs or noises, which result from by Sir Charles Bell, Weber, Sir William Hamilton and otherstheir combination. Simple tones also constitute a qualitative con- concerning motor presentations proper, a very different view, first tinuum, but it has only one dimension, their so-called "pitch "; tentatively advanced by the great physiologist Johannes Müller, and adopted by Helmholtz, Wundt, and especially by Bain, long this may be represented by a straight line ranging between two prevailed. It is, however, now generally discredited, if not com more or less indefinite extremes. If intensity, that is to say pletely overthrown. According to this view," the characteristic loudness, is taken into account, we have of course a continuum feeling of exerted force" must be regarded, Bain maintained," not of two dimensions. The tone-continuum is also universally as arising from an inward transmission but as the concomitant regarded as steadily diminishing in massiveness or extensity of the outgoing current by which the muscles are stimulated to act as the pitch rises. And, in fact, as we approach the lower (op. cit. p. 79). The necessity for this assumption has certainly not been established on physiological grounds, nor apparently did Bain As a matter of fact there are no objects absolutely black, none rely primarily on these; for at the very outset of his discussion we that are devoid of all lustre and completely absorbent of light. But find him saying "that action is a more intimate and inseparable this does not affect the argument. It is assumed that the physiological differentiation of the retina property of our constitution than any of our sensations, and enters as a component part into every one of our senses (op. cit. p. 59). has advanced from the centre, where vision is most distinct, towards But this important psychological truth is affirmed as strenuously by the margin where it is least so; and it is found that stimulation of some, at any rate (e.g. Professor James) of Bain's opponents as it was the margin yields none but achromatic sensations, stimulation of a by Bain himself. Unhappily many, under the same psychophysical certain intermediate zone only sensations of yellow or blue, and central stimulation alone sensations of every hue. Further, total Cf. Bastian, The Brain as an Organ of Mind (1880), pp. 691 sqq.; colour-blindness is extremely rare, whereas red-green colour-blind-Ferrier, The Functions of the Brain (1886), 2nd ed. pp. 382 999.; ness is comparatively common. James, Principles of Psychology (1890), ch. xxvi.