CHAPTER VII - PSYCHIC GRADATIONS

Summary

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.