Produced by Clare Graham & Marc D'Hooghe at Free Literature (Images generously made available by the Hathi Trust) THE PRINCIPLES OF PSYCHOLOGY BY WILLIAM JAMES PROFESSOR OF PSYCHOLOGY IN HARVARD UNIVERSITY IN TWO VOLUMES VOL II. NEW YORK HENRY HOLT AND COMPANY 1918 CONTENTS. CHAPTER XVII. SENSATION Its distinction from perception. Its cognitive function--acquaintance with qualities. No pure sensations after the first days of life. The 'relativity of knowledge'. The law of contrast. The psychological and the physiological theories of it. Hering's experiments. The 'eccentric projection' of sensations. CHAPTER XVIII. IMAGINATION Our images are usually vague. Vague images not necessarily general notions. Individuals differ in imagination; Gabon's researches. The 'visile' type, 58. The 'audile' type. The 'motile' type. Tactile images, 65. The neural process of imagination. Its relations to that of sensation. CHAPTER XIX. THE PERCEPTION OF 'THINGS' Perception and sensation. Perception is of definite and probable things. Illusions;--of the first type;--of the second type. The neural process in perception. 'Apperception'. Is perception an unconscious inference? Hallucinations, 114. The neural process in hallucination. Binet's theory. 'Perception-time'. CHAPTER XX. THE PERCEPTION OF SPACE The feeling of crude extensity. The perception of spatial order. Space-'relations'. The meaning of localization. 'Local signs'. The construction of 'real' space. The subdivision of the original sense-spaces. The sensation of motion over surfaces. The measurement of the sense-spaces by each other. Their summation. Feelings of movement in joints. Feelings of muscular contraction. Summary so far. How the blind perceive space. Visual space. Helmholtz and Reid on the test of a sensation. The theory of identical points. The theory of projection. Ambiguity of retinal impressions;--of eye-movements. The choice of the visual reality. Sensations which we ignore. Sensations which seem suppressed. Discussion of Wundt's and Helmholtz's reasons for denying that retinal sensations are of extension. Summary. Historical remarks. CHAPTER XXI. THE PERCEPTION OF REALITY Belief and its opposites. The various orders of reality. 'Practical' realities. The sense of our own bodily existence is the nucleus of all reality. The paramount reality of sensations. The influence of emotion and active impulse on belief. Belief in theories. Doubt. Relations of belief and will. CHAPTER XXII. REASONING 'Recepts'. In reasoning, we pick out essential qualities. What is meant by a mode of conceiving. What is involved in the existence of general propositions. The two factors of reasoning. Sagacity. The part played by association by similarity. The intellectual contrast between brute and man: association by similarity the fundamental human distinction. Different orders of human genius. CHAPTER XXIII. THE PRODUCTION OF MOVEMENT