The Principles of Psychology, Volume 2

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

The diffusive wave. Every sensation produces reflex effects on the whole organism.

CHAPTER XXIV.

INSTINCT

Its definition. Instincts not always blind or invariable. Two principles of non-uniformity in instincts: 1) Their inhibition by habits; 2) Their transitoriness. Man has more instincts than any other mammal. Reflex impulses. Imitation. Emulation. Pugnacity. Sympathy. The hunting instinct. Fear. Acquisitiveness. Constructiveness. Play. Curiosity. Sociability and shyness. Secretiveness. Cleanliness. Shame. Love. Maternal love.

CHAPTER XXV.

THE EMOTIONS

Instinctive reaction and emotional expression shade imperceptibly into each other. The expression of grief; of fear; of hatred. Emotion is a consequence, not the cause, of the bodily expression. Difficulty of testing this view. Objections to it discussed. The subtler emotions, 468. No special brain-centres for emotion. Emotional differences between individuals. The genesis of the various emotions.

CHAPTER XXVI.

WILL

Voluntary movements: they presuppose a memory of involuntary movements. Kinæsthetic impressions, 488. No need to assume feelings of innervation. The 'mental cue' for a movement may be an image of its visual or auditory effects as well as an image of the way it feels. Ideo-motor action. Action after deliberation. Five types of decision. The feeling of effort. Unhealthiness of will: 1) The explosive type; 2) The obstructed type. Pleasure and pain are not the only springs of action. All consciousness is impulsive. What we will depends on what idea dominates in our mind. The idea's outward effects follow from the cerebral machinery. Effort of attention to a naturally repugnant idea is the essential feature of willing. The free-will controversy. Psychology, as a science, can safely postulate determinism, even if free-will be true. The education of the Will. Hypothetical brain-schemes.

CHAPTER XXVII.

HYPNOTISM

Modes of operating and susceptibility. Theories about the hypnotic state. The symptoms of the trance.

CHAPTER XXVIII.

NECESSARY TRUTHS AND THE EFFECTS OF EXPERIENCE

Programme of the chapter. Elementary feelings are innate. The question refers to their combinations. What is meant by 'experience'. Spencer on ancestral experience. Two ways in which new cerebral structure arises: the 'back-door' and the 'front-door' way. The genesis of the elementary mental categories. The genesis of the natural sciences. Scientific conceptions arise as accidental variations. The genesis of the pure sciences. Series of evenly increasing terms. The principle of mediate comparison. That of skipped intermediaries. Classification. Predication. Formal logic. Mathematical propositions. Arithmetic. Geometry. Our doctrine is the same as Locke's. Relations of ideas v. couplings of things The natural sciences are inward ideal schemes with which the order of nature proves congruent. Metaphysical principles are properly only postulates. Æsthetic and moral principles are quite incongruent with the order of nature. Summary of what precedes. The origin of instincts. Insufficiency of proof for the transmission to the next generation of acquired habits. Weismann's views. Conclusion.

INDEX.

PSYCHOLOGY.

CHAPTER XVII.

SENSATION.

After inner perception, outer perception! The next three chapters will treat of the processes by which we cognize at all times the present world of space and the material things which it contains. And first, of the process called Sensation.

SENSATION AND PERCEPTION DISTINGUISHED.

The words Sensation and Perception do not carry very definitely discriminated meanings in popular speech, and in Psychology also their meanings run into each other. Both of them name processes in which we cognize an objective world; both (under normal conditions) need the stimulation of incoming nerves ere they can occur; Perception always involves Sensation as a portion of itself; and Sensation in turn never takes place in adult life without Perception also being there. They are therefore names for different cognitive functions, not for different sorts of mental fact. The nearer the object cognized comes to being a simple quality like 'hot,' 'cold,' 'red,' 'noise,' 'pain,' apprehended irrelatively to other things, the more the state of mind approaches pure sensation. The fuller of relations the object is, on the contrary; the more it is something classed, located, measured, compared, assigned to a function, etc., etc.; the more unreservedly do we call the state of mind a perception, and the relatively smaller is the part in it which sensation plays.

Sensation, then, so long as we take the analytic point of view, differs from Perception only in the extreme simplicity of its object or content. Its function is that of mere acquaintance with a fact. Perception's function, on the other hand, is knowledge about a fact; and this knowledge admits of numberless degrees of complication. But in both sensation and perception we perceive the fact as an immediately present outward reality, and this makes them differ from 'thought' and 'conception,' whose objects do not appear present in this immediate physical way. From the physiological point of view both sensations and perceptions differ from 'thoughts' (in the narrower sense of the word) in the fact that nerve-currents coming in from the periphery are involved in their production. In perception these nerve-currents arouse voluminous associative or reproductive processes in the cortex; but when sensation occurs alone, or with a minimum of perception, the accompanying reproductive processes are at a minimum too.

I shall in this chapter discuss some general questions more especially relative to Sensation. In a later chapter perception will take its turn. I shall entirely pass by the classification and natural history of our special 'sensations,' such matters finding their proper place, and being sufficiently well treated, in all the physiological books.

THE COGNITIVE FUNCTION OF SENSATION.

A pure sensation is an abstraction; and when we adults talk of our 'sensations' we mean one of two things: either certain objects, namely simple qualities or attributes like hard, hot, pain; or else those of our thoughts in which acquaintance with these objects is least combined with knowledge about the relations of them to other things. As we can only think or talk about the relations of objects with which we have acquaintance already, we are forced to postulate a function in our thought whereby we first become aware of the bare immediate natures by which our several objects are distinguished. This function is sensation. And just as logicians always point out the distinction between substantive terms of discourse and relations found to obtain between them, so psychologists, as a rule, are ready to admit this function, of the vision of the terms or matters meant, as something distinct from the knowledge about them and of their relations inter se. Thought with the former function is sensational, with the latter, intellectual. Our earliest thoughts are almost exclusively sensational.