CHAPTER VII

PSYCHIC GRADATIONS

Psychological Unity of Organic Nature--Material Basis of the Soul: Psychoplasm--Scale of Sensation--Scale of Movement--Scale of Reflex Action--Simple and Compound Reflex Action--Reflex Action and Consciousness--Scale of Perception--Unconscious and Conscious Perception--Scale of Memory--Unconscious and Conscious Memory--Association of Perceptions--Instinct--Primary and Secondary Instincts--Scale of Reason--Language--Emotion and Passion--The Will--Freedom of the Will

The great progress which psychology has made, with the assistance of evolution, in the latter half of the century culminates in the recognition of _the psychological unity of the organic world_. Comparative psychology, in co-operation with the ontogeny and phylogeny of the _psyche_, has enforced the conviction that organic life in all its stages, from the simplest unicellular protozoon up to man, springs from the same elementary forces of nature, from the physiological functions of sensation and movement. The future task of scientific psychology, therefore, is not, as it once was, the exclusively subjective and introspective analysis of the highly developed mind of a philosopher, but the objective, comparative study of the long gradation by which man has slowly arisen through a vast series of lower animal conditions. This great task of separating the different steps in the psychological ladder, and proving their unbroken phylogenetic connection, has only been seriously attempted during the last ten years, especially in the splendid work of Romanes. We must confine ourselves here to a brief discussion of a few of the general questions which that gradation has suggested.

All the phenomena of the psychic life are, without exception, bound up with certain material changes in the living substance of the body, the _protoplasm_. We have given to that part of the protoplasm which seems to be the indispensable substratum of psychic life the name of _psychoplasm_ (the "soul-substance," in the monistic sense); in other words, we do not attribute any peculiar "essence" to it, but we consider the _psyche_ to be merely _a collective idea of all the psychic functions of protoplasm_. In this sense the "soul" is merely a physiological abstraction like "assimilation" or "generation." In man and the higher animals, in accordance with the division of labor of the organs and tissues, the psychoplasm is a differentiated part of the nervous system, the _neuroplasm_ of the ganglionic cells and their fibres. In the lower animals, however, which have no special nerves and organs of sense, and in the plants, the psychoplasm has not yet reached an independent differentiation. Finally, in the unicellular protists, the psychoplasm is identified either with the whole of the living protoplasm of the simple cell or with a portion of it. In all cases, in the lowest as well as the highest stages of the psychological hierarchy, a certain chemical composition and a certain physical activity of the psychoplasm are indispensable before the "soul" can function or act. That is equally true of the elementary psychic function of the plasmatic sensation and movement of the protozoa, and of the complex functions of the sense-organs and the brain in the higher animals and man. The activity of the psychoplasm, which we call the "soul," is always connected with metabolism.

All living organisms, without exception, are sensitive; they are influenced by the condition of their environment, and react thereon by certain modifications in their own structure. Light and heat, gravity and electricity, mechanical processes and chemical action in the environment, act as _stimuli_ on the sensitive psychoplasm, and effect changes in its molecular composition. We may distinguish the following five chief stages of this sensibility:

I. At the lowest stage of organization the _whole psychoplasm_, as such, is sensitive, and reacts on the stimuli from without; that is the case with the lowest protists, with many plants, and with some of the most rudimentary animals.

II. At the second stage very simple and undiscriminating _sense-organs_ begin to appear on the surface of the organism, in the form of protoplasmic filaments and pigment spots, the forerunners of the nerves of touch and the eyes; these are found in some of the higher protists and in many of the lower animals and plants.

III. At the third stage _specific organs_ of sense, each with a peculiar adaptation, have arisen by differentiation out of these rudimentary processes: there are the chemical instruments of smell and taste, and the physical organs of touch, temperature, hearing, and sight. The "specific energy" of these sense-organs is not an original inherent property of theirs, but has been gained by functional adaptation and progressive heredity.

IV. The fourth stage is characterized by the _centralization_ or integration of the _nervous system_, and, consequently, of sensation; by the association of the previously isolated or localized sensations presentations arise, though they still remain unconscious. That is the condition of many both of the lower and the higher animals.

V. Finally, at the fifth stage, the highest psychic function, _conscious perception_, is developed by the mirroring of the sensations in a central part of the nervous system, as we find in man and the higher vertebrates, and probably in some of the higher invertebrates, notably the articulata.

All living organisms without exception have the faculty of _spontaneous movement_, in contradistinction to the rigidity and inertia of unorganized substances (_e.g._, crystals); in other words, certain changes of place of the particles occur in the living psychoplasm from internal causes, which have their source in its own chemical composition. These active vital movements are partly discovered by direct observation and partly only known indirectly, by inference from their effects. We may distinguish five stages of them.

I. At the lowest stage of organic life, in the chromacea, and many protophyta and lower metaphyta, we perceive only those _movements of growth_ which are common to all organisms. They are usually so slow that they cannot be directly observed; they have to be inferred from their results--from the change in size and form of the growing organism.

II. Many protists, particularly unicellular algæ of the groups of diatomacea and desmidiacea, accomplish a kind of creeping or swimming motion by _secretion_, by ejecting a slimy substance at one side.

III. Other organisms which float in water--for instance, many of the radiolaria, siphonophora, ktenophora, and others--ascend and descend by altering their _specific gravity_, sometimes by osmosis, sometimes by the separation or squeezing-out of air.

IV. Many plants, especially the sensitive plants (mimosa) and other papilionacea, effect movements of their leaves or other organs by _change of pressure_--that is, they alter the strain of the protoplasm, and, consequently, its pressure on the enclosing elastic walls of the cells.

V. The most important of all organic movements are the _phenomena of contraction_--_i.e._, changes of form at the surface of the organism, which are dependent on a twofold displacement of their elements; they always involve two different conditions or phases of motion--contraction and expansion. Four different forms of this plasmatic contraction may be enumerated:

(_a_) Amoeboid movement (in rhizopods, blood-cells, pigment-cells, etc.).

(_b_) A similar flow of protoplasm within enclosed cells.

(_c_) Vibratory motion (ciliary movements) in infusoria, spermatozoa, ciliated epithelial cells.

(_d_) Muscular movement (in most animals).

The elementary psychic activity that arises from the combination of sensation and movement is called _reflex_ (in the widest sense), reflective function, or _reflex action_. The movement--no matter what kind it is--seems in this case to be the immediate result of the _stimulus_ which evoked the sensation; it has, on that account, been called stimulated motion in its simplest form (in the protists). All living protoplasm has this feature of irritability. Any physical or chemical change in the environment may, in certain circumstances, act as a stimulus on the psychoplasm, and elicit or "release" a movement. We shall see later on how this important physical concept of "releasing" directly connects the simplest organic reflex actions with similar mechanical phenomena of movement in the inorganic world (for instance, in the explosion of powder by a spark, or of dynamite by a blow). We may distinguish the following seven stages in the scale of reflex action:

I. At the lowest stage of organization, in the lowest protists, the stimuli of the outer world (heat, light, electricity, etc.) cause in the indifferent protoplasm only those indispensable movements of growth and nutrition which are common to all organisms, and are absolutely necessary for their preservation. That is also the case in most of the plants.

II. In the case of many freely moving protists (especially the amoeba, the heliozoon, and the rhizopod) the stimuli from without produce on every spot of the unprotected surface of the unicellular organism external movements which take the form of changes of shape, and sometimes changes of place (amoeboid movement, pseudopod formation, the extension and withdrawal of what look like feet); these indefinite, variable processes of the protoplasm are not yet permanent organs. In the same way, general organic irritability takes the form of indeterminate reflex action in the sensitive plants and the lowest metazoa; in many multicellular organisms the stimuli may be conducted from one cell to another, as all the cells are connected by fine fibres.

III. Many protists, especially the more highly developed protozoa, produce on their unicellular body two little organs of the simplest character--an organ of touch and an organ of movement. Both these instruments are direct external projections of protoplasm; the stimulus, which alights on the first, is immediately conducted to the other by the psychoplasm of the unicellular body, and causes it to contract. This phenomenon is particularly easy to observe, and even produce experimentally, in many of the stationary infusoria (for instance, the _poteriodendron_ among the flagellata, and the _vorticella_ among the ciliata). The faintest stimulus that touches the extremely sensitive hairs, or _cilia_, at the free end of the cells, immediately causes a contraction of a thread-like stalk at the other, fixed end. This phenomenon is known as a "simple reflex arch."

IV. These phenomena of the unicellular organism of the infusoria lead on to the interesting mechanism of the neuro-muscular cells, which we find in the multicellular body of many of the lower metazoa, especially in the cnidaria (polyps and corals). Each single neuro-muscular cell is a "unicellular reflex organ"; it has on its surface a sensitive spot, and a motor muscular fibre inside at the opposite end; the latter contracts as soon as the former is stimulated.

V. In other cnidaria, notably in the free swimming medusæ--which are closely related to the stationary polyps--the simple neuro-muscular cell becomes two different cells, connected by a filament; an external _sense-cell_ (in the outer skin) and an internal _muscular cell_ (under the skin). In this _bicellular reflex organ_ the one cell is the rudimentary organ of sensation, the other of movement; the connecting bridge of the psychoplasmic filament conducts the stimulus from one to the other.

VI. The most important step in the gradual construction of the reflex mechanism is the division into three cells; in the place of the simple connecting bridge we spoke of there appears a third independent cell, the _soul-cell_, or ganglionic cell; with it appears also a new psychic function, _unconscious presentation_, which has its seat in this cell. The stimulus is first conducted from the sensitive cell to this intermediate presentative or psychic cell, and then issued from this to the motor muscular cell as a mandate of movement. These _tricellular reflex organs_ are preponderantly developed in the great majority of the invertebrates.

VII. Instead of this arrangement we find in most of the vertebrates a _quadricellular reflex organ_, two distinct "soul-cells," instead of one, being inserted between the sensitive cell and the motor cell. The external stimulus, in this case, is first conducted centripetally to the sensitive cell (the sensible psychic cell), from this to the _will-cell_ (the motor psychic cell), and from this, finally, to the contractile muscular cell. When many such reflex organs combine and new psychic cells are interposed we have the intricate reflex mechanism of man and the higher vertebrates.

The important distinction which we make, in morphology and physiology, between unicellular and multicellular organisms holds good for their elementary psychic activity, reflex action. In the unicellular protists (both the plasmodomous primitive plants, or _protophyta_, and the plasmophagous primitive animals, or _protozoa_) the whole physical process of reflex action takes place in the protoplasm of one single cell; their "cell-soul" seems to be a unifying function of the psychoplasm of which the various phases only begin to be seen separately when the differentiation of special organs sets in.

The second stage of psychic activity, compound reflex action, begins with the cenobitic protists (_v.g._, the volvox and the carchesium). The innumerable social cells, which make up this cell-community or coenobium, are always more or less connected, often directly connected by filamentous bridges of protoplasm. A stimulus that alights on one or more cells of the community is communicated to the rest by means of the connecting fibres, and may produce a general contraction. This connection is found, also, in the tissues of the multicellular animals and plants. It was erroneously believed at one time that the cells of vegetal tissue were completely isolated from each other, but we have now discovered fine filaments of protoplasm throughout, which penetrate the thick membranes of the cells, and maintain a material and psychological communication between their living plasmic contents. That is the explanation of the mimosa: when the tread of the passer-by shakes the root of the plant, the stimulus is immediately conveyed to all the cells, and causes a general contraction of its tender leaves and a drooping of the stems.

An important and universal feature of all reflex phenomena is the absence of consciousness. For reasons which we shall give in the tenth chapter we only admit the presence of consciousness in man and the higher animals, not in plants, the lower animals, and the protists; consequently all stimulated movements in the latter must be regarded as reflex--that is, all movements which are not _spontaneous_, not the outcome of internal causes (impulsive and automatic movements).[14] It is different with the higher animals which have developed a centralized nervous system and elaborate sense-organs. In these cases consciousness has been gradually evolved from the psychic reflex activity, and now conscious, voluntary action appears, in opposition to the still continuing reflex action below. However, we must distinguish two different processes, as we did in the question of instinct--primary and secondary reflex action. Primary reflex actions are those which have never reached the stage of consciousness in phyletic development, and thus preserve the primitive character (by heredity from lower animal forms). Secondary reflex actions are those which were conscious, voluntary actions in our ancestors, but which afterwards became unconscious from habit or the lapse of consciousness. It is impossible to draw a hard and fast line in such cases between conscious and unconscious psychic function.

Older psychologists (Herbart, for instance) considered "presentation" to be the fundamental psychic phenomenon, from which all the others are derived. Modern comparative psychology endorses this view in so far as it relates to the idea of _unconscious_ presentation; but it considers _conscious_ presentation to be a secondary phenomenon of mental life, which is entirely wanting in plants and the lower animals, and is only developed in the higher animals. Among the many contradictory definitions which psychologists have given of "presentation," we think the best is that which makes it consist in an internal picture of the external object which is given us in sensation--an "idea," in the broader sense. We may distinguish the following four stages in the rising scale of presentative function:

I. _Cellular presentation._--At the lowest stages we find presentation to be a general physiological property of psychoplasm; even in the simplest unicellular protist sensations may leave a permanent trace in the psychoplasm, and these may be reproduced by memory. In more than four thousand kinds of radiolaria, which I have described, every single species is distinguished by special, hereditary skeletal structure. The construction of this specific, and often highly elaborate, skeleton by a cell of the simplest description (generally globular) is only intelligible when we attribute the faculty of presentation, and, indeed, of a special reproduction of the plastic "feeling of distance," to the constructive protoplasm--as I have pointed out in my _Psychology of the Radiolaria_.[15]

II. _Histionic presentation._--In the coenobia or cell-colonies of the social protists, and still better in the tissues of plants and lower, nerveless animals (sponges, polyps, etc.), we find the second stage of unconscious presentation, which consists of the common psychic activity of a number of closely connected cells. If a single stimulus may, instead of simply spending itself in the reflex movement of an organ (the leaf of a plant, for instance, or the arm of a polyp), leave a permanent impression, which can be spontaneously reproduced later on, we are bound to assume, in explaining the phenomenon, a histionic presentation, dependent on the psychoplasm of the associated tissue-cells.

III. _Unconscious presentation in the ganglionic cells._--This third and higher stage of presentation is the commonest form the function takes in the animal world; it seems to be a localization of presentation in definite "soul-cells." In its simplest form it appears at the sixth stage of reflex action, when the tricellular reflex organ arises: the seat of presentation is then the intermediate psychic cell, which is interposed between the sensitive cell and the muscular cell. With the increasing development of the animal nervous system and its progressive differentiation and integration, this unconscious presentation also rises to higher stages.

IV. _Conscious presentation in the cerebral cells._--With the highest stage of development of the animal organization consciousness arises, as a special function of a certain central organ of the nervous system. As the presentations are conscious, and as special parts of the brain arise for the association of these conscious presentations, the organism is qualified for those highest psychic functions which we call thought and reflection, intellect and reason. Although the tracing of the phyletic barrier between the older, unconscious, and the younger, conscious, presentation is extremely difficult, we can affirm, with some degree of probability, that the evolution of the latter from the former was _polyphyletic_; because we find conscious and rational thought, not only in the highest forms of the vertebrate stem (man, mammals, birds, and a part of the lower vertebrates), but also in the most highly developed representatives of other animal groups (ants and other insects, spiders and the higher crabs among the articulata, cephalopods among the mollusca).

The evolutionary scale of memory is closely connected with that of presentation; this extremely important function of the psychoplasm--the condition of all further psychic development--consists essentially in the _reproduction of presentations_. The impressions in the bioplasm, which the stimulus produced as sensations, and which became presentations in remaining, are revived by memory; they pass from potentiality to actuality. The latent potential energy of the psychoplasm is transformed into kinetic energy. We may distinguish four stages in the upward development of memory, corresponding to the four stages of presentation.

I. _Cellular memory._--Thirty years ago Ewald Hering showed "memory to be a general property of organized matter" in a thoughtful work, and indicated the great significance of this function, "to which we owe almost all that we are and have." Six years later, in my work on _The Perigenesis of the Plastidule, or the Undulatory Origin of the Parts of Life: an Experiment in the Mechanical Explanation of Elementary Evolutionary Processes_, I developed these ideas, and endeavored to base them on the principles of evolution. I have attempted to show in that work that unconscious memory is a universal and very important function of all _plastidules_; that is, of those hypothetical molecules, or groups of molecules, which Naegeli has called _micellae_, others _bioplasts_, and so forth. Only _living_ plastidules, as individual molecules of the active protoplasm, are reproductive, and so gifted with memory; that is the chief difference between the organic and inorganic worlds. It might be stated thus: "Heredity is the memory of the plastidule, while variability is its comprehension." The elementary memory of the unicellular protist is made up of the molecular memory of the plastidules or _micellae_, of which its living cell-body is constructed. As regards the extraordinary performances of unconscious memory in these unicellular protists, nothing could be more instructive than the infinitely varied and regular formation of their defensive apparatus, their shells and skeletons; in particular, the diatomes and cosmaria among the protophytes, and the radiolaria and thalamophora among the protozoa, afford an abundance of most interesting illustrations. In many thousand species of these protists the specific form which is inherited is _relatively constant_, and proves the fidelity of their unconscious cellular memory.

II. _Histionic memory._--Equally interesting examples of the second stage of memory, the unconscious memory of tissues, are found in the heredity of the individual organs of plants and the lower, nerveless animals (sponges, etc.). This second stage seems to be _a reproduction of the histionic presentations_, that association of cellular presentations which sets in with the formation of coenobia in the social protists.

III. In the same way we must regard the third stage, the unconscious memory of those animals which have a nervous system, as a reproduction of the corresponding "unconscious presentations" which are stored up in certain ganglionic cells. In most of the lower animals all memory is unconscious. Moreover, even in man and the higher animals, to whom we must ascribe consciousness, the daily acts of unconscious memory are much more numerous and varied than those of the conscious faculty; we shall easily convince ourselves of that if we make an impartial study of a thousand unconscious acts we perform daily out of habit, and without thinking of them, in walking, speaking, writing, eating, and so forth.

IV. Conscious memory, which is the work of certain brain-cells in man and the higher animals, is an "internal mirroring" of very late development, the highest outcome of the same psychic reproduction of presentations which were mere unconscious processes in the ganglionic cells of our lower animal ancestors.

The concatenation of presentations--usually called the association of ideas--also runs through a long scale, from the lowest to the highest stages. This, too, is originally and predominantly unconscious ("instinct"); only in the higher classes of animals does it gradually become conscious ("reason"). The psychic results of this "association of ideas" are extremely varied; still, a very long, unbroken line of gradual development connects the simplest unconscious association of the lowest protist with the elaborate conscious chain of ideas of the civilized man. The _unity of consciousness_ in man is given as its highest consequence (Hume, Condillac). All higher mental activity becomes more perfect in proportion as the normal association extends to more numerous presentations, and in proportion to the order which is imposed on them by the "criticism of pure reason." In dreams, where this criticism is absent, the association of the reproduced impressions often takes the wildest forms. Even in the work of the poetic imagination, which constructs new groups of images by varying the association of the impressions received, and in hallucinations, etc., they are often most unnaturally arranged, and seem to the prosaic observer to be perfectly irrational. This is especially true of supernatural "forms of belief," the apparitions of spiritism, and the fantastic notions of the transcendental dualist philosophy; though it is precisely these _abnormal associations_ of "faith" and of "revelation" that have often been deemed the greatest treasures of the human mind (cf. chap. xvi.).

The antiquated psychology of the Middle Ages (which, however, still numbers many adherents) considered the mental life of man and that of the brute to be two entirely different phenomena; the one it attributed to "reason," the other to "instinct." In harmony with the traditional story of creation, it was assumed that each animal species had received a definite, unconscious psychic force from the Creator at its formation, and that this instinct of each species was just as unchangeable as its bodily structure. Lamarck proved the untenableness of this error in 1809 by establishing the theory of Descent, and Darwin completely demolished it in 1859. He proved the following important theses with the aid of his theory of selection:

1. The instincts of species show individual differences, and are just as subject to modification under the law of _adaptation_ as the morphological features of their bodily structure.

2. These modifications (generally arising from a change of habits) are partly transmitted to offspring by _heredity_, and thus accumulate and are accentuated in the course of generations.

3. _Selection_, both artificial and natural, singles out certain of these inherited modifications of the psychic activity; it preserves the most useful and rejects the least adaptive.

4. The _divergence_ of psychic character which thus arises leads, in the course of generations, to the formation of new instincts, just as the divergence of morphological character gives rise to new species.

Darwin's theory of instinct is now accepted by most biologists; Romanes has treated it so ably, and so greatly expanded it in his distinguished work on _Mental Evolution in the Animal World_, that I need merely refer to it here. I will only venture the brief statement that, in my opinion, there are instincts in _all_ organisms--in all the protists and plants as well as in all the animals and in man; though in the latter they tend to disappear in proportion as reason makes progress at their expense.

The two chief classes of instincts to be differentiated are the primary and secondary. Primary instincts are the common lower impulses which are unconscious and inherent in the psychoplasm from the commencement of organic life; especially the impulses to self-preservation (by defence and maintenance) and to the preservation of the species (by generation and the care of the young). Both these fundamental instincts of organic life, _hunger_ and _love_, sprang up originally in perfect unconsciousness, without any co-operation of the intellect or reason. It is otherwise with the _secondary_ instincts. These were due originally to an intelligent adaptation, to rational thought and resolution, and to purposive conscious action. Gradually, however, they became so automatic that this "other nature" acted unconsciously, and, even through the action of heredity, seemed to be "innate" in subsequent generations. The consciousness and deliberation which originally accompanied these particular instincts of the higher animals and man have died away in the course of the life of the plastidules (as in "abridged heredity"). The unconscious purposive actions of the higher animals (for instance, their mechanical instincts) thus come to appear in the light of innate impulses. We have to explain in the same way the origin of the "_à priori_ ideas" of man; they were originally formed empirically by his predecessors.[16]

In the superficial psychological treatises which ignore the mental activity of animals and attribute to man only a "true soul," we find him credited also with the exclusive possession of reason and consciousness. This is another trivial error (still to be found in many a manual, nevertheless) which the comparative psychology of the last forty years has entirely dissipated. The higher vertebrates (especially those mammals which are most nearly related to man) have just as good a title to "reason" as man himself, and within the limits of the animal world there is the same long chain of the gradual development of reason as in the case of humanity. The difference between the reason of a Goethe, a Kant, a Lamarck, or a Darwin, and that of the lowest savage, a Veddah, an Akka, a native Australian, or a Patagonian, is much greater than the graduated difference between the reason of the latter and that of the most "rational" mammals, the anthropoid apes, or even the papiomorpha, the dog, or the elephant. This important thesis has been convincingly proved by the thoroughly critical comparative work of Romanes and others. We shall not, therefore, attempt to cover that ground here, nor to enlarge on the distinction between the reason and the intellect; as to the meaning and limits of these concepts philosophic experts give the most contradictory definitions, as they do on so many other fundamental questions of psychology. In general it may be said that the process of the formation of concepts, which is common to both these cerebral functions, is confined to the narrower circle of concrete, proximate associations in the intellect, but reaches out to the wider circle of abstract, more comprehensive groups of associations in the work of reason. In the long gradation which connects the reflex actions and the instincts of the lower animals with the reason of the highest, intellect precedes the latter. And there is the fact, of great importance to our whole psychological treatise, that even these highest of our mental faculties are just as much subject to the laws of heredity and adaptation as are their respective organs; Flechsig pointed out in 1894 that the "organs of thought," in man and the higher mammals, are those parts of the cortex of the brain which lie between the four inner sense-centres (cf. chapters x. and xi.).

The higher grade of development of ideas, of intellect and reason, which raises man so much above the brute, is intimately connected with the rise of language. Still here also we have to recognize a long chain of evolution which stretches unbroken from the lowest to the highest stages. Speech is no more an exclusive prerogative of man than reason. In the wider sense, it is a common feature of all the higher gregarious animals, at least of all the articulata and the vertebrates, which live in communities or herds; they need it for the purpose of understanding each other and communicating their impressions. This is effected either by touch or by signs, or by sounds having a definite meaning. The song of the bird or of the anthropoid ape (_hylobates_), the bark of the dog, the neigh of the horse, the chirp of the cricket, the cry of the cicada, are all specimens of animal speech. Only in man, however, has that articulate conceptual speech developed which has enabled his reason to attain such high achievements. Comparative philology, one of the most interesting sciences that has arisen during the century, has shown that the numerous elaborate languages of the different nations have been slowly and gradually evolved from a few simple primitive tongues (Wilhelm Humboldt, Bopp, Schleicher, Steinthal, and others). August Schleicher, of Jena, in particular, has proved that the historical development of language takes place under the same phylogenetic laws as the evolution of other physiological faculties and their organs. Romanes (1893) has expanded this proof, and amply demonstrated that human speech, also, differs from that of the brute only in _degree_ of development, not in essence and kind.

The important group of psychic activities which we embrace under the name of "emotion" plays a conspicuous part both in theoretical and practical psychology. From our point of view they have a peculiar importance from the fact that we clearly see in them the direct connection of cerebral functions with other physiological functions (the beat of the heart, sense-action, muscular movement, etc.); they, therefore, prove the unnatural and untenable character of the philosophy which would essentially dissociate psychology from physiology. All the external expressions of emotional life which we find in man are also present in the higher animals (especially in the anthropoid ape and the dog); however varied their development may be, they are all derived from the two elementary functions of the _psyche_, sensation and motion, and from their combination in reflex action and presentation. To the province of sensation, in a wide sense, we must attribute the feeling of _like_ and _dislike_ which determines the emotion; while the corresponding _desire_ and _aversion_ (love and hatred), the effort to attain what is liked and avoid what is disliked, belong to the category of movement. "Attraction" and "repulsion" seem to be the sources of _will_, that momentous element of the soul which determines the character of the individual. The _passions_, which play so important a part in the psychic life of man, are but intensifications of emotion. Romanes has recently shown that these also are common to man and the brute. Even at the lowest stage of organic life we find in all the protists those elementary feelings of like and dislike, revealing themselves in what are called their _tropisms_, in the striving after light and darkness, heat or cold, and in their different relations to positive and negative electricity. On the other hand, we find at the highest stage of psychic life, in civilized man, those finer shades of emotion, of delight and disgust, of love and hatred, which are the mainsprings of civilization and the inexhaustible sources of poetry. Yet a connecting chain of all conceivable gradations unites the most primitive elements of feeling in the psychoplasm of the unicellular protist with the highest forms of passion that rule in the ganglionic cells of the cortex of the human brain. That the latter are absolutely amenable to physical laws was proved long ago by the great Spinoza in his famous _Statics of Emotion_.

The notion of _will_ has as many different meanings and definitions as most other psychological notions--presentation, soul, mind, and so forth. Sometimes will is taken in the widest sense as a _cosmic attribute_, as in the "World as will and presentation" of Schopenhauer; sometimes it is taken in its narrowest sense as an _anthropological attribute_, the exclusive prerogative of man--as Descartes taught, for instance, who considered the brute to be a mere machine, without will or sensation. In the ordinary use of the term, _will_ is derived from the phenomenon of voluntary movement, and is thus regarded as a psychic attribute of most animals. But when we examine the will in the light of comparative physiology and evolution, we find--as we do in the case of sensation--that it is a universal property of living psychoplasm. The automatic and the reflex movements which we observe everywhere, even in the unicellular protists, seem to be the outcome of inclinations which are inseparably connected with the very idea of life. Even in the plants and lowest animals these inclinations, or tropisms, seem to be the joint outcome of the inclinations of all the combined individual cells.

But when the "tricellular reflex organ" arises (page 115), and a third independent cell--the "psychic," or "ganglionic," cell--is interposed between the sense-cell and the motor cell, we have an independent elementary organ of will. In the lower animals, however, this will remains _unconscious_. It is only when consciousness arises in the higher animals, as the subjective mirror of the objective, though internal, processes in the neuroplasm of the psychic cells, that the will reaches that highest stage which likens it in character to the human will, and which, in the case of man, assumes in common parlance the predicate of "liberty." Its free dominion and action become more and more deceptive as the muscular system and the sense-organs develop with a free and rapid locomotion, entailing a correlative evolution of the brain and the organs of thought.

The question of the liberty of the will is the one which has more than any other cosmic problem occupied the time of thoughtful humanity, the more so that in this case the great philosophic interest of the question was enhanced by the association of most momentous consequences for practical philosophy--for ethics, education, law, and so forth. Emil du Bois-Reymond, who treats it as the seventh and last of his "seven cosmic problems," rightly says of the question: "Affecting everybody, apparently accessible to everybody, intimately involved in the fundamental conditions of human society, vitally connected with religious belief, this question has been of immeasurable importance in the history of civilization. There is probably no other object of thought on which the modern library contains so many dusty folios that will never again be opened." The importance of the question is also seen in the fact that Kant put it in the same category with the questions of the immortality of the soul and belief in God. He called these three great questions the indispensable "postulates of practical reason," though he had already clearly shown them to have no reality whatever in the light of _pure_ reason.

The most remarkable fact in connection with this fierce and confused struggle over the freedom of the will is, perhaps, that it has been theoretically rejected, not only by the greatest critical philosophers, but even by their extreme opponents, and yet it is still affirmed to be self-evident by the majority of people. Some of the first teachers of the Christian Churches--such as St. Augustine and Calvin--rejected the freedom of the will as decisively as the famous leaders of pure materialism, Holbach in the eighteenth and Büchner in the nineteenth century. Christian theologians deny it, because it is irreconcilable with their belief in the omnipotence of God and in predestination. God, omnipotent and omniscient, saw and willed all things from eternity--he must, consequently, have predetermined the conduct of man. If man, with his free will, were to act otherwise than God had ordained, God would not be all-mighty and all-knowing. In the same sense Leibnitz, too, was an unconditional determinist. The monistic scientists of the last century, especially Laplace, defended determinism as a consequence of their mechanical view of life.

The great struggle between the determinist and the indeterminist, between the opponent and the sustainer of the freedom of the will, has ended to-day, after more than two thousand years, completely in favor of the determinist. The human will has no more freedom than that of the higher animals, from which it differs only in degree, not in kind. In the last century the dogma of liberty was fought with general philosophic and cosmological arguments. The nineteenth century has given us very different weapons for its definitive destruction--the powerful weapons which we find in the arsenal of comparative physiology and evolution. We now know that each act of the will is as fatally determined by the organization of the individual and as dependent on the momentary condition of his environment as every other psychic activity. The character of the inclination was determined long ago by _heredity_ from parents and ancestors; the determination to each particular act is an instance of _adaptation_ to the circumstances of the moment wherein the strongest motive prevails, according to the laws which govern the statics of emotion. Ontogeny teaches us to understand the evolution of the will in the individual child. Phylogeny reveals to us the historical development of the will within the ranks of our vertebrate ancestors.