Page:Popular Science Monthly Volume 35.djvu/404

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expend their influence directly upon muscles, they may, neverthetheless, be regarded as a part of the motor machinery, since they act on other centers which are motor; and, by the associated action of these two kinds of centers, the will gradually acquires a real though limited control over the voluntary muscles.

Volition, whatever its origin, involves a state of excitation of the brain and stimulation of body and mind. Opposition only serves to increase its energy (as the load in "the nerve-muscle preparation"[1] augments the force of the contraction), and under excitement intellectual as well as muscular work is more easily done. Emotional excitement, if not of too absorbing a nature, promotes intellectual activity, but the latter is itself accompanied by a peculiar exaltation of feeling which is a source of the keenest psychical satisfaction.

Stimulation, then, either sensory or volitional, is a necessary antecedent of activity—in common parlance, its cause. Prof. Bain advocates the idea that stimulation is the sole cause of pleasure, the nutritive functions by keeping up the vital energy enabling stimulation to be carried to certain lengths before degenerating into pain. If we fall short of the pain limit, we fail of the satisfactions which flow from the conscious expenditure of energy to the full degree of which the organism is capable. If we exceed this limit, we pay the penalty of physical degeneracy and resulting mental decrepitude with the accompanying falling off of activity, and hence of pleasure. Degeneration also follows from disuse—that is, the neglect of stimulation, and consequent inaction.

Sir William Hamilton, following Aristotle, defines pleasure as "the reflex of the spontaneous and unimpeded exertion of power of whose energy we are conscious." But exercise of power occurs as a result of stimulation. The larger statement of Prof. Bain, therefore, includes that of Hamilton; and, since the spontaneous exertion of power with the accompanying state of consciousness depends on excitation of motor centers, both these statements are involved in my sixth thesis, viz., that movements are the primary source of pleasure and pain which, in the experience school of psychology, are recognized as the basis of the entire mental life.

Mr. James Ward[2] regards the reflex movements immediately expressive of pleasure and pain as primordial, the voluntary movements being elaborated out of these. But movements occur presumably below the plane of consciousness—e. g., in vegetable protoplasm. We may therefore conclude that, in the developing animal series, the lowest members of which are indistinguishable

  1. The calf-muscle, with its nerves, taken from the leg of a frog. Within certain limits, the heavier the weight attached to the muscle the more powerfully it contracts when the nerve is stimulated.
  2. Loc. cit.