how far Fechner derived his psychophysics from experience, how far from fallacies of inference, from his romantic imagination and from his theosophic metaphysics, which indeed coloured his whole book on psychophysics. At the very outset he started with his previous metaphysical hypothesis of parallelistic identity without interaction. He now compared the spiritual and bodily sides of a man to the concave and convex sides of a circle, as inner and outer sides of the same process, which is psychical as viewed from within and physical as viewed from without. He also maintained throughout the book that physical and psychical energy do not interfere, but that the psychical is, like a mathematical quantity, a function of the physical, depending upon it, and vice versa, only in the sense that a constant relation according to law exists, such that we may conclude from one to the other, but without one ever being cause of the other. By his psychophysics he meant the exact doctrine of the relations of dependency between physical and psychical. The name was new, but not the doctrine. From antiquity men had applied themselves to determine the relations between the physical stimuli and the so-called “quality” of sensations. But what was new was the application of this doctrine to the relations between the stimuli and the so-called “intensity” of sensations. He generalized Weber’s law (q.v.) in the form that sensation generally increases in intensity as the stimulus increases by a constant function of the previous stimulus; or increases in an arithmetical progression as the stimulus increases in a geometrical ratio; or increases by addition of the same amount as the stimulus increases by the same multiple; or increases as the logarithm of the stimulus. There are then, at least within the limits of moderate sensations, concomitant variations between stimuli and sensations, not only in “quality,” as in the intervals of sounds, which were understood long ago, but also in “intensity”; and the discovery of the latter is the importance of Weber’s and Fechner’s law. By the rules of induction from concomitant variations, we are logically bound to infer the realistic conclusion that outer physical stimuli cause inner sensations of sensible effects. But, unfortunately for Fechner, the very opposite conclusion followed from the presuppositions of his parallelistic metaphysics, and from the Leibnitzian view of the conservation of energy, which he was the first in our time to use in order to argue that a physical cause cannot produce a psychical effect, on the ground that physical energy must be exactly replaced by physical energy.
Having satisfied himself in what he called “outer psychophysics,” that the stimulus causes only the nervous process and not sensation, he passed to what he called “inner psychophysics,” or the theory of the relation between nervous and psychical processes. He rightly argued against the old theory that the continuity of nervous processes in the brain is interrupted by mental processes of thought and will: there is a nervous process for every mental process. But two questions then arose. What is the relation between nervous process and sensation? What causes sensation? The first question he answered from his imagination by supposing that, while the external world is stimulus of the nervous process, the nervous process is the immediate stimulus of the sensation, and that the sensation increases by a constant fraction of the previous stimulus in the nervous system, when Weber’s law proves only that it increases by a constant fraction of the previous stimulus in the external world. The second question he answered from his parallelistic metaphysics by deducing that even within the organism there is only a constant dependency of sensation on nervous process without causation, because the nervous process is physical but the sensation psychical. This answer supposed that the whole physical process from the action of the external stimulus on the nervous system to the reaction of the organism on the external world is one series, while the conscious process beginning with sensation is only parallel and as it were left high and dry. What then is the cause of the sensation? Huxley, it will be remembered, in similar circumstances, answered this question by degrading consciousness to an epiphenomenon, or bye-product of the physical process. Fechner was saved from this absurdity, but only to fall into the greater absurdity of his own panpsychism. Having long assumed that the whole world is animated throughout, and that there are always two parallel series, physical and psychical, he concluded that, while a physical stimulus is causing a physical nervous process, a psychical accompaniment of the stimulus is causing the sensation, which, according to him, is the psychical accompaniment of the nervous process; and that, as the whole physical and the whole psychical series are the same, differing only as outer and inner, this identity holds both of stimulus and its psychical accompaniment and of nervous process and its accompanying sensation. Accordingly, he calls these and all other processes “psychophysical”; and as he recognized two parallel energies, physical and psychical, differing only as outer and inner aspects of the same energy, he called this “psychophysical energy.” In such a philosophy all reality is “psychophysical.” At the same time Fechner would not have us suppose that the two sides are equal; according to him, the psychical, being the psychophysical as viewed from within, is real, the physical, being the psychophysical viewed from without, is apparent; so in oneself, though nervous process and psychical process are the same, it is the psychical which is the reality of which the nervous is mere appearance; and so everywhere, spirit is the reality, body the appearance of spirit to spirit. Finally, he supposed that one spirit is in another, and all in the highest spirit, God. By this means also he explained unconsciousness. In point of fact, many stimuli are beneath the “threshold” of a man’s consciousness. Leibnitz, in the Nouveaux Essais, ii. 11, had also said that we have many “petites perceptions,” of which we are unconscious, and had further suggested that a perception of which we are, is composed of a quantity of “petites perceptions” of which we are not, conscious. Proceeding on this suggestion, and misled by the mathematical expression which he had given to Weber’s law, Fechner held that a conscious sensation, like its stimulus, consists of units, or elements, by summation and increments of which conscious sensations and their differences are produced; so that consciousness, according to this unnecessary assumption, emerges from an integration of unconscious shocks or tremors. But by the hypothesis of the inclusion of spirit in spirit, he was further able to hold that what is unconscious in one spirit is conscious in a higher spirit, while everything whatever is in the consciousness of the highest spirit of God, who is the whole of reality of which the spirits are parts, while the so-called physical world is merely outer appearance of one spirit to another.
Fechner first confused physics and metaphysics in psychophysics, and next proceeded to confuse them again in his work on evolution (Einige Ideen zur Schöpfungs und Entwicklungs-geschichte der Organismen, 1873). He perceived that Darwinism attributed too much to accident, and was also powerless to explain the origin of life and of consciousness. But his substitute was his own hypothesis of panpsychism, from which he deduced a “cosmorganic” evolution from a “cosmorganic” or original condition of the world as a living organism into the inorganic, by the principle of tendency to stability. The world, as he thought, on its physical side, always was a living body; and on its psychical side God always was its conscious spirit; and, so far from life arising from the lifeless, and consciousness from unconsciousness, the life and consciousness of the whole world are the origin of the lifeless and the unconscious in parts of it, by a kind of secondary automatism, while we ourselves are developed from our own mother-earth by differentiation. By thus supposing a psychical basis to evolution, Fechner, anticipating Wundt, substituted a psychical development of organs for Darwinian accidental variation. The difficulty of such speculations is to prove that things apparently dead and mindless are living souls. Their interest to the metaphysician is their opposition to physics on the one hand and to theism on the other. Shall we resign our traditional belief that the greater part of the world is mere body, but that its general adaptability to conscious organisms proves its creation and government by God, and take to the new hypothesis, which, by a transfer of design from God to Nature, supposes that everything physical is alive, and conducts its life by psychical impulses of its own? Fechner himself went even further, and together with design transferred God Himself to Nature. This is the subject of his last metaphysical work, Die Tagesansicht gegenüber der Nachtansicht (1879). The “day-view” (Fechner’s) is the view that God is the psychophysical all-embracing being, the law and consciousness of the world. It resembles the views of Hegel and Lotze in its pantheistic tendency. But it does not, like theirs, sacrifice our personality; because, according to Fechner, the one divine consciousness includes us as a larger circle includes smaller circles. By this ingenious suggestion of the membership of one spirit in another, Fechner’s “day-view” also puts Nature in a different position; neither with Hegel sublimating it to the thought of God’s mind, nor with Lotze degrading it to the phenomena of our human minds, but identifying it with the outer appearance of one spirit to another spirit in the highest of spirits.
We have dwelt on this curious metaphysics of Fechner because it contains the master-key to the philosophy of the present moment. When the later reaction to Kant arose against both Hegelianism and materialism, the nearly contemporary appearance of Fechner’s Psychophysics began to attract experimental psychologists by its real as well as its apparent exactness, and both psychologists and metaphysicians by its novel way of putting the relations between the physical and the psychical in man and in the world. Fechner saw psychology deriving advantage from the methods, as well as the results, of his experiments, and in 1879 the first psychological laboratory was erected by Wundt at Leipzig. But he had also to endure countless objections to his mathematical statement of Weber’s law, to his unnecessary assumption of units of sensation, and to his unjustifiable transfer of the law from physical to physiological stimuli of sensations, involving in his opinion his parallelistic view of body and mind. Among psychologists Helmholtz, Mach, Brentano, Hering, Delboeuf, were all more or less against him. Sigwart in his Logic has also opposed the parallelistic view itself; and James has criticized it from the point of view that the soul selects out of the possibilities of the brain means to its own ends. Nevertheless, largely under the influence of the exaggeration
