are again connected with more distant nerves. Anil when studying nerve - function,, we saw that a disturb- ance set up by an afferent nerve in its ganglion, does not affect exclusively the efferent nerve., but that part of it, conveyed through centripetal and commissural nerves, affects other centres, and these again others, until it has reverberated throughout the entire nervous system. "What follows? These reverberations are feeble disturb ances. And every centre, liable as it is to be strongly disturbed through its afferent or centripetal nerve, is liable also to be feebly disturbed by these reverberations arriving through other nerves. What then must happen with each of the libero-rtwtor elements composing those higher centres in which nervous changes become changes of consciousness? "When it is affected through the direct and fully-opened route, by that peripheral impression to which it stands organically related, it evolves much molecular motion, becomes an active propagator of disturbances throughout the nervous system, and is the seat of what we call a real feeling; but when it is affected by these secondary waves diffused from other strongly excited parts, it becomes, as compared with them (or with itself under the previous condition) a generator of but little molecular motion, and is the seat of that faint feeling which we distinguish as ideal. In brief, those vivid states of consciousness which we know as sensations, accompany direct and therefore strong excitations of nerve- centres; while the faint states of consciousness which we know as remembered sensations, or ideas of sensations, accompany indirect, and therefore weak, excitations of the same nerve-centres.
That the contrast of intensity between the effects of direct and indirect excitations, though it holds generally, does not hold without exception, is a fact quite reconcilable with this interpretation. For, on the one hand, a direct excitation may be very feeble; while, on the other hand, through a concurrence of diffused disturbances, an indirect excitation may rise to considerable strength. Hence, oc- casionally, an ideal feeling will become almost or quite equal in vividness to a real feeling. Especially may this happen when the nerve-centre concerned is surcharged with blood; since a small disturbance may then set up in it an amount of change equal to that which a great disturbance produces when only the ordinary quantity of blood is pre- sent. And it is a matter of observation that congested nerve-centres are those in which indirectly-excited feelings reach an intensity scarcely less than that of directly-excited feelings.
When we pass from the feelings called sensations, of which the strong forms are peripherally initiated, to the feelings called emotions, of which the strong forms are centrally initiated, we find the difference between the strong and the weak forms by no means so great; so that, in fact, ideal emotion passes into actual emotion without any line of de- marcation. Obviously this is what might be anticipated. For whether ideal or actual, emotion is an accompaniment of an indirect excitation: it is not an immediate result of peripheral impressions, either simple or combined; but a mediate or remote result of them. Hence, all emo- tions, vivid and faint, being the subjective aspects of ob- jective nervous changes that are produced indirectly, are distinguishable only according to the degree of indirectness of the excitation, and this admits of insensible gradations.
§ 50. One more general truth must be set down to com- plete the outline. The foregoing inferences joined with some contained in the last chapter, introduce us to it.
IT §§ 36, 37, it was pointed out that nerve-centres dis- integrated by action, are perpetually re-integrating them- selves, and again becoming fit for action. We saw that repair partially makes up for waste from instant to instant, and that the arrears of repair are made up daily during that period of quiescence when waste almost ceases.
126 THE 'DATA OF PSYCHOLOGY.
further saw that the restoration of a nerve-centre to its st??to of integrity, is not only the filling up of its quantum of de- composable matter, but is also the replacing of molecules most exposed to disturbance, and consequently the produc- tion of a comparatively-unstable state. And we saw how, after a period of profound repose, there thus arises a con- - dition of the nerve-centres such that very slight stimuli cause nervous discharges.
This law applies not generally only, but specially to each nerve-centre and each of its component parts. In propor- tion as any part of a nerve-centre has been for a long time unused — in proportion, that is, as repair of it has gone on day after day and night after night unhindered by appre- ciable waste, it must be brought to a state of more than ordinary instability — a state of excessive readiness to de- compose and discharge. What must happen? In common with all other parts, it is exposed to these reverberations which from instant to instant fill the nervous system. Its extreme instability must render it unusually sensitive to these reverberations — unusually ready to undergo change, - to yield up molecular motion, and to become the seat of ^ the concomitant ideal feeling. Besides a great liability to the ideal feeling this same condition must entail a great strength of it; and so while the instability continues, a strong ideal feeling will be perpetually aroused. As, however, the nerve-centre in which such secondary mole- cular changes and accompanying ideal feelings are thus set up, is somewhat wasted by them, it follows that after they have gone on for a considerable period the instability of the centre will be diminished: it will no longer be so easily decomposed by indirect disturbances, and the jfeeling will not be produced. - ' " Here we have the interpretation of what are called lesires. Desires are^ ideal feelings that arise when^tho *eal feelin^To^liicli they correspond have not been jx- ^rienced for some time. They are then liable to be excited by various of tlie indirect disturbances reflected from part1 to part of the nervous system. They are usually vivid and persistent in proportion to the previous period of rest — - more vivid and more persistent than ideal feelings of the same kind under ordinary conditions. But after a pro- longed period during which they continue to arise and almost monopolize consciousness, they become feebler and finally die away.
§ 51. Such are the leading truths of -ZEstho-Physiology, set forth with as much fulness as is here requisite. Sensa- tion and emotion in their relations to nervous action,, have been dealt with generally; and whatever has been said of special sensations and special emotions has been said merely to illustrate a law which holds among all the rest. The concomitants,, subjective and objective,, of each particular kind of sensation and each particular kind of emotion, I here pass over. They may be studied to great advantage in the works of Professor Bain on The Senses and the Intellect, and _ The. Emotions and the Will; in which he has given an elaborate account of the connection between each particular feeling, simple or complex, and its various physical accompaniments. To these works I must com- mend the reader who wishes to trace out these minor cor- relations. As data for the present treatise, the only facts needful to be carried with us are those set forth in the preceding sections. They may be summed up thus.
Feeling of whatever kind is directly known by each person in no other place than his own consciousness. That feelings exist in the world beyond consciousness, is a belief reached only through an involved combination of infer- ences. That., alike in human and inferior beings, feelings are accompaniments of changes in the peculiar strujoture known as the nervous system, is also an jncliTec.tLy- established belief. And that the feelings alone cognizable by any individual are products of the action of his own 128 THE DATA OF PSYCHOLOGY.
i*ervous system,, which lie has never seen and on whicli he can try no experiments, is a belief only to be arrived at through a farther chain of reasoning. Nevertheless, the evidence, though so indirect, is so extensive, so varied, and so congruous, that we may accept the conclusion without hesitation.
The conclusion having been accepted — provisionally if not permanently — its validity is shown by leading us to anticipate truly, in one set of cases after another, the par- ticular subjective phenomena that accompany particular objective phenomena. We have seen that the several circumstances which facilitate or hinder nervous action, are also circumstances which facilitate or hinder feeling. We have seen that as nervous action occupies appreciable time, so feeling occupies appreciable time. We have seen that each feeling leaves a partial incapacity for a like feel- ing, as each nervous action leaves a partial incapacity for a like nervous action. We have seen that, other things equal, the intensities of feelings vary as the intensities of the correlative nervous actions. We have seen that the difference between direct and indirect nervous disturbances, corresponds to the difference between the vivid feelings we call real and the faint feelings we call idea^ And we have seen that certain more special objective phenomena which nervous actions present, have answering subjective phenomena in the forms of feeling we distinguish as desires.
Thus, impossible as it is to get immediate proof that 'feeling andjiervous action are the inner and outer faces of *^3^^S^9]i^9.£eJ £e* the, hypothesis that they are so harmonizes with all the observed facts; and, as elsewhere shown (Mrst Principles,. § 4QJ. no other verification is pos- sible for us than that wEict results from the establishment of complete congruity among our experiences.
CHAPTEE YIL THE SCOPE OF PSYCHOLOGY.
§ 52. We may now enter on our special topic. Tims far we Have been occupied with the data of Psychology, and not with Psychology properly so-called. Here leaving the foundations we pass to the superstructure.
Not a few readers will be surprised by the assertion that none of the truths we have been contemplating are psycho- logical truths. Since the anatomy and physiology of the nervous system have occupied so much attention, and since it has been growing manifest that there is a fundamental connection between nervous changes and psychical, states, there has arisen a confusion between the phenomena which underlie Psychology and the phenomena of Psychology itself. In reality, all the facts ascertained by those who have made nerve- structure and nerve-function.their studies, are facts of a simpler order than those rightly termed psychological; though they are facts entering into the composition of psychological facts.
Most will admit without hesitation that the first five chapters.of this part consist o£ propositions which are exclu- sively. mQx.pholqgical and physiological. In them TTJfe "struc- ture of the nervous system, its functions, the conditions to its action, &c., have been dealt with purely as physical phenomena — phenomena as purely physical as the absorption K j 130 THE DATA OF PSYCHOLOGY.
of nutriment or the circulation of the "blood. Whatever ' ' implications may have arisen from the use of words that carry with them indirect meanings,, the direct meanings of all the propositions set down have nowhere implied con- sciousness or feeling; and, ignoring consciousness or feeling, they have left out that which is tacitly or avowedly contained in every proposition of Psychology.
It will probably be thought, however, that at any rate truths belonging to Psychology proper are to be found in the last chapter. Dealing as the last chapter does with the connections between nervous changes and feelings, it necessarily becomes, by including a psychical element, a part of psychical science. To this the rejoinder is that, though it can scarcely be excluded absolutely from the body of this science, yet it does not strictly fall within that body. ^Estho- physiology has a position that is entirely unique. It belongs neither to the objective world nor the subjective world; but i taking a term from each, occupies itself with the correlation , j1 of the two. It may with as much propriety be included in the domain of physical science as in the domain of psy- chical science j and must be left where it stands, as the 1, link between them.
j * Perhaps this explanation will increase rather than decrease the surprise produced by the assertion that was to be justi- fied. To clear up the confusion, we must examine more carefully the distinction between the truths which are strictly psychological and those which merely enter into the composition of psychological truths.
§ 53. Throughout the preceding chapters, including even the last, every proposition set down has expressed some relation of phenomena occurring within the limits of the organism. The subject-matter has been the character of a structure; or the effect which a disturbance set up in one *" place has in causing motion in another; or the connection between the physical state of the whole or a part of the THE SCOPE OF PSYCHOLOGY.
organism,, and some general or local nervous process; or the variable intensity of an action in a nerve -centre as determined by a preceding like action; or the interdepen- dence of internal physical changes and internal psychical changes. That is to say,, the attention has everywhere been directed exclusively to co-existences and sequences of which the body alone is the sphere. Distinct or tacit reference has, indeed,, frequently been made to some external force. Either a disturbing agent lying beyond the limits of the organism has been referred to in general terms, 01% for illustration's sake,, this or the other kind of disturbing agent has been named. But such references, vague or distinct, have been made merely because it was needful to suppose something by which an organic change was set up; not because this something had to be included in the proposi-- tion set down, which in eveiy case formulated an internal relation only. The entanglement of phenomena is such, that we can never cut off absolutely from all others the par- ticular phenomena we are dealing with; but,, because we presuppose these other phenomena, it does not follow that the science to which they pertain forms part of the science with which we are specially occupied. For instance, it is impossible to describe, or think of, a chemical' experiment that discloses some chemical relation, without making dis- tinct or tacit references to physical relations — the pouring and mixture of liquids, the ascent of bubbles of disengaged gas, the falling of a precipitate; but it is not therefore held that we are including physics in our chemistry. Similarly, it must be admitted that though the foregoing chapters have tacitly assumed environing forces, yet this assumption has been simply incidental to the study of internal co- existences and sequences.
Now so long as we state facts o£ which all the terms lie? within the organism, our facts are morphological or phy- siological and in no degree psychological. Even though the relation with which we are dealing is that between a 132 THE DATA OF PSYCHOLOGY.
change and a feeling, it is still not a psychological relation so long as the feeling is regarded merely as con- nected with the nervous change, and not as connected with some existence lying outside the organism. As certainly as the man who demonstrates by dissection the articulations of the bones, and the man who, by a sphygmograph, delineates the varying motions of the heart, are respectively studying morphology and physiology; so certainly is the man who examines nervous structure and experiments on nervous function, a student of these same sciences,, if he considers the inner correlations only and does not simultaneously consider the answering outer correlations.
For that which distinguishes Psychology from the sciences on which it rests,, is, that each of its propositions takes ac- count both of the connected internal phenomena and of the connected external phenomena to which they refer. In a phy- siological proposition an inner relation is the essential sub- ject of thought; but in a psychological proposition an outer relation is joined with it as a co-essential subject of thought. A relation in the environment rises into co-ordinate im- portance with a relation in the organism. The thing con- templated is now a totally different thing. It is not the connection between the internal phenomena, nor is it the connection between the external phenomena; but it is the connection between these two connections. A psychological proposition is necessarily compounded of two propositions, of which one concerns the subject and the other concerns the object; and cannot be expressed without the four terms which these two propositions imply. The distinction may be best explained by symbols. Suppose that A and B are two related manifestations in the environment — say,, the colour and taste of a fruit; then, so long as we contemplate their relation by itself, or as associated with other external phenomena, we are occupied with a portion of physical science. Isow suppose that a and b are the sensations pro- duced in the organism by this peculiar light which the fruit THE SCOPE OF PSYCHOLOGY. 133 reflects, and by tlie cliemical action of its juice on tlio palate \ then, so long as we study the action of the light on the retina and optic centres, and consider how the juice sets up in other centres a nervous change known as sweetness, we are occupied with facts belonging to the sciences of Physiology and JEstho-physiology. Bat we pass into the domain of Psychology the moment we inquire how there comes to exist within the organism a relation between a and b that in some way or other corresponds to the relation between A and B. Pyschology is exclusively concerned with this connection between (A B) and (a 6) — has to investigate its nature, its origin, its meaning, &c.
A moment's introspection will now make it clear to the reader, that he cannot frame any psychological conception without thus looking at internal co-existences and se- quences in their adjustments to external co-existences and sequences. If he studies the simplest act of per- ception, as that of localizing a touch in some part of IPS skin, the indispensable terms of his inquiry are: — on the one hand a thing (1) and a position (2), both of which he regards as objective; and on the other hand a sensation (3), and a state of consciousness constituting his apprehen- sion of position (4), both of which he regards as subjective. Again, to cite an example from the opposite extreme, if he takes for his problem one of his involved sentiments, as that of justice, he cannot represent to himself this sentiment, or give any meaning to its name, without calling to mind actions and relations supposed to exist in the environment: neither this nor any other emotion can be aroused in consciousness even vaguely, without positing something beyond consciousness to which it refers. And when, instead of studying Psychology subjectively, he studies it objectively in the acts of other beings, he similarly finds himself incapable of stirring a step without thinking of inner correlations in their references to outer correlations.
]<3t THE DATA OF PSYCHOLOGY.
§ 54. It is contended by some that Psychology is a part of Biology, and should be merged in it; and those who hold this view will possibly answer the above argument by saying that in many cases the non-psychological part of Biology also takes into account phenomena in the environ- ment^ and even definite connections among these pheno- mena. The life of every organism is a continuous adaptation of its inner actions to outer actions; and a complete interpretation of the inner actions involves recognition of the outer actions. The annual production of leaves, flowers, and seeds by plants, is adjusted to the annual changes of the seasons; and there is in animals an adjust- ment between external changes in temperature and abund- ance, and internal production of ova. Moreover, there are many special relations of structure and function in plants and animals, that have reference to special relations of struc- ture and function in surrounding plants and animals: in- stance those arrangements of the sexual organs that fit particular phsenoganis for being fertilized by the particular insects that visit them.
But ferae as is this conception of Life (and having based the Principles of Biology on it I am not likely to question or to undervalue it), I nevertheless hold the distinction above drawn to be substantially valid. For through- out Biology proper, the environment and its correlated phenomena are either but tacitly recognized, or, if overtly and definitely recognized, are so but occasionally; while the organism and its correlated phenomena practically monopolize the attention. But in Psychology, the cor- related phenomena of the environment are at every step avowedly and distinctly recognized; and are as essential to every psychological idea as are the correlated phe- nomena of the organism. Let us observe the contrast as exemplified.. We study digestion. Digestion implies food. Food implies neighbouring plants or animals. But this implication scarcely enters into our study of digestion, THE SCOFE OF PSYCHOLOGY. 135 unless we ask the quite special question — liow the digestive organs become fitted to the materials they have to act upon? Again, when we interpret respiration we take for granted a surrounding oxygenated medium. And yet to show how far the two may be separated, we need only remember that the phenomena of respiration may be very well traced out in one who breathes a bladder of gas artificially obtained from peroxide of manganese or chlorate of potash. Once more, if, in following out the life-history of a plant, we have to note the adaptation of its hooked seeds to the woolly fleece of the animal which accidentally carries them, off and disperses them, this distinct reference to specially- connected phenomena in the environment, occurs either but once in an account of the plant's life, or only at long intervals. In fact, we may say that the great mass of purely biological pheno- mena may be displayed for some time by an organism de- tached from its medium, as by a fish out of water. Now observe how different it is with psychological phenomena. We cannot explain a single act of a fish as it moves about in the water,, without taking into account its relations to neighbouring -objects distinguished by specially-related attributes. The instinctive proceedings of the insect, equally with those which in higher creatures we call in- telligent, we are unable even to express without referring to things around.
In brief, then, the propositions of Biology, when they imply the environment at all, imply almost exclusively its few general and constant phenomena, which, because of their generality and constancy, may be left out of con- sideration; whereas the propositions of Psychology refer to its multitudinous, special, and ever- varying phenomena, which, because of their speciality and changeability, can- not be left out of consideration.
§ 55. The admission that Psychology is not demarcated; from Biology by a sharp line, will perhaps be construed; 136 THE DATA OF PSYCHOLOGY.
into tie admission that it cannot rightly be regarded as a * distinct science. But those who so construe the admission, misconceive the natures of the relations among the sciences. They assume that there exist objectively those clear separa- tions which the needs of classification lead us to make .subjectively. Whereas the fact is, that beyond the divisions between the three fundamental orders of the sciences, Ab- stract, Abstract-concrete, and Concrete, there exist ob- ^ jec lively no clear separations at all: there are only differ- ;. ent groups of phenomena broadly contrasted but shading " off one into another. To those who accept the doctrine of Evolution, this scarcely needs saying; for Evolution being a universal process, one and continuous throughout all forms of existence, there can be no break — no change from one group of concrete phenomena to another without a bridge of intermediate phenomena. It will be well here, 3 however, to show by illustrations that the simpler concrete sciences are separable from one another only in the same I way that Psychology is separable from Biology.
* Astronomy and Geology are regarded as distinct. But I Geology is nothing more than a chapter continuing in i detail one part of a history that was once wholly astrono- I mic; and even now, many of its leading facts belong as I much to the older part of the history as to the younger.
[ Not only do we trace back the Earth to a time when its ' astronomic attributes were uncomplicated by those geoj logic ones that have gradually arisen as it cooled; not only ,, in the solar heat, causing the aerial, marine, and fluvial i 4 currents which work most geologic changes, are we com-