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.