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~ILLUSIONS~

_A PSYCHOLOGICAL STUDY_

BY JAMES SULLY AUTHOR OF "SENSATION AND INTUITION," "PESSIMISM," ETC.

THIRD EDITION

LONDON KEGAN PAUL, TRENCH & CO., 1, PATERNOSTER SQUARE 1887

(_The rights of translation and of reproduction are reserved_)

~THE INTERNATIONAL SCIENTIFIC SERIES.~

VOL. XXXIV.

PREFACE.

The present volume takes a wide survey of the field of error, embracing in its view not only the illusions of sense dealt with in treatises on physiological optics, etc., but also other errors familiarly known as illusions, and resembling the former in their structure and mode of origin. I have throughout endeavoured to keep to a strictly scientific treatment, that is to say, the description and classification of acknowledged errors, and the explanation of these by a reference to their psychical and physical conditions. At the same time, I was not able, at the close of my exposition, to avoid pointing out how the psychology leads on to the philosophy of the subject. Some of the chapters were first roughly sketched out in articles published in magazines and reviews; but these have been not only greatly enlarged, but, to a considerable extent, rewritten. J. S.

_Hampstead, April, 1881._

CONTENTS.

CHAPTER I.

THE STUDY OF ILLUSION.

Vulgar idea of Illusion, 1, 2; Psychological treatment of subject, 3, 4; definition of Illusion, 4-7; Philosophic extension of idea, 7, 8.

CHAPTER II.

THE CLASSIFICATION OF ILLUSIONS.

Popular and Scientific conceptions of Mind, 9, 10; Illusion and Hallucination, 11-13; varieties of Immediate Knowledge, 13-16; four-fold division of Illusions, 16-18.

CHAPTER III.

ILLUSIONS OF PERCEPTION: GENERAL.

_Psychology of Perception_:--The Psychological analysis of Perception, 19, 20; Sensation and its discrimination, etc., 20, 21; interpretation of Sensation, 22, 23; construction of material object, 23, 24; recognition of object, specific and individual, 24-27; Preperception and Perception, 27-31; Physiological conditions of Perception, 31-33; Visual and other Sense-perception, 33, 34.

_Illusions of Perception_:--Illusion of Perception defined, 35-38; sources of Sense-illusion, 38-40: (a) confusion of Sense-impression, 40-44; (b) misinterpretation of Sense-impression, 44; Passive and Active misinterpretation, 44-46; Passive Illusions as organically and extra-organically conditioned, 46-49.

CHAPTER IV.

ILLUSIONS OF PERCEPTION--_continued_.

A. _Passive Illusions (a) as determined by the Organism._ _Results of Limits of Sensibility_:--Relation of quantity of Sensation to that of Stimulus, 50-52; coalescence of simultaneous Sensations, 52-55; after-effect of Stimulation, 55, 56; effects of prolonged Stimulation, 56-58; Specific Energy of Nerves, 58, 59; localization of Sensation, 59-62; Subjective Sensations, 62-64.

Table of contents (by pages)

• 1: Illusions by James Sully
• 2: Subordination of Sense impression to Preperception
• 3: Illusions of Introspection defined
• 4: Genesis of illusory opinion of self
• 5: The psychologist has a different interest in the subject
• 6: To false or illusory perceptions
• 7: The classification of illusions
• 8: While hallucination is a total displacement
• 9: Hallucinations have such a basis of fact
• 10: In calling these four forms of cognition immediate
• 11: Illusions of perception general
• 12: Be this process of classifying
• 13: Which is the most instantaneous
• 14: The identification of a friend
• 15: The process of preperception may be shortened
• 16: And the stage of preperception becomes evanescent
• 17: Distinguished as the passive stage of preperception
• 18: How shall we define an illusion of perception
• 19: Understanding sense illusion in this way
• 20: Together with those varying tactual and motor feelings
• 21: And the process of preperception being controlled by this
• 22: The fusion of nervous processes must have another cause
• 23: ILLUSIONS OF PERCEPTION continued
• 24: To carry over the retinal result of the movement
• 25: Beget palpable illusion in another way
• 26: Whatever the nature of the stimulus
• 27: And not of the peripheral fibre
• 28: May rightly be named an hallucination
• 29: States of anaesthesia lead to odd illusions among the insane
• 30: The pressure of a body on the retina
• 31: If an artificial auricle is placed in front of the ears
• 32: And not unfrequently produce illusion
• 33: By means of the now familiar stereoscope
• 34: By such signs as linear perspective and cast shadow
• 35: The scrap inside no longer wears the complementary hue
• 36: Rather than the convex into the concave
• 37: When I look at a brick viaduct a mile or two off
• 38: Of looking at the distant viaduct
• 39: Even if the preperception be correct
• 40: Voluntary Selection of Interpretation
• 41: See the diagonal step like pattern
• 42: The indistinct and indefinite shapes of the masses of rock
• 43: It shows itself more distinctly
• 44: For instance hardly feel the illusion at all
• 45: Giving a vivid anticipation of tickling
• 46: We will now pass to a second mode of illusory expectation
• 47: The first I shall call rudimentary
• 48: Like the incomplete hallucinations
• 49: Fully developed persistent hallucinations
• 50: Develop into full hallucinatory percepts
• 51: In the case of passive illusions
• 52: The illusion seems an impossibility
• 53: To be drawn from our waking experience
• 54: The retardation of the circulation
• 55: From the physiological point of view
• 56: Be unrestricted by collision with external fact
• 57: Let us first glance at the action of such external stimuli
• 58: Maury found that when his lips were tickled
• 59: The physiologist Gruithuisen had a dream
• 60: A sense impression is instantly discriminated and classed
• 61: The interpretation is effected by means of a visual image
• 62: Be allowable to speak of this as an hallucination
• 63: Whether that of a present peripheral stimulation
• 64: And so far not to be haphazard or wholly chaotic
• 65: After puzzling over this dream
• 66: We may become aware of the process of coalescence
• 67: This is the basis of harmony in lyrical poetry
• 68: A lady friend of mine once dreamt that she was in church
• 69: Predisposing them to such concerted action
• 70: Clearly involve a measure of volitional guidance
• 71: The intellectual sentiment of consistency
• 72: But the street strewn with rich nosegays
• 73: To order the chaotic of which I have been speaking
• 74: Three undergraduates got out of the coach
• 75: And when the mind is in a more or less somnolent condition
• 76: A strong susceptibility to the hypnotic influence
• 77: Illusions of Introspection defined
• 78: The term introspective knowledge must
• 79: Confusion of Internal and External Experience
• 80: To transfix any particular feeling of the moment
• 81: Since they depend largely on representation
• 82: Which is so prominent a factor in introspective illusion
• 83: And our highest emotional experiences
• 84: Value of the Introspective Method
• 85: An ingredient of representation
• 86: The cognition of the quality is instantaneous
• 87: Any attribution of objective worth is illusory
• 88: Though sometimes approaching the intuitive form
• 89: A fertile source of illusory insight is
• 90: And this predisposition will be the more powerful
• 91: The bias to illusory insight is still more powerful
• 92: That these illusions of insight
• 93: Of such immediate representative cognition
• 94: Whereas perception is partly representative
• 95: In so far as recognition is assimilation
• 96: By the fact of previous mnemonic revivals
• 97: Very vaguely and imperfectly localized
• 98: What I have called a mnemonic image
• 99: Or of what may be called mnemonic perspective
• 100: Such an imaginative reproduction
• 101: When we look at an object foreshortened in perspective
• 102: Wundt says that when once a tedious waiting is over
• 103: Occur at every distinguishable fraction of time
• 104: When sudden and deeply agitating
• 105: That I am able to dismiss the illusion
• 106: Our minds are such refracting media
• 107: Some of them seem to our mature minds very oddly selected
• 108: The error is one of perception
• 109: An illusion of memory is apt to multiply itself
• 110: So we may mark off two classes of mnemonic hallucination
• 111: Are these false and illegitimate sources of mnemonic images
• 112: They may give rise to something like permanent illusions
• 113: Any recital of another's experience
• 114: And so give rise to apparently personal recollections
• 115: Involves an illusory sense of continuity
• 116: There are the frequently recurring higher feelings
• 117: Seems at the moment to rupture the bond of identity
• 118: A distinct recollection is substantially correct
• 119: Momentary illusions of self consciousness
• 120: Some mode of inference from these
• 121: Simple Illusory Belief Expectation
• 122: I confidently anticipate a thunderstorm
• 123: An illusory expectation may arise
• 124: Here we reach the full development of illusory expectation
• 125: The unknown recesses of the remote future offer
• 126: The thing to note is that such retrospective beliefs
• 127: Seems one indivisible cognition
• 128: Where the illusory element is still more striking
• 129: As an impulse of self assertion
• 130: Of aiming at individual happiness
• 131: And consequently to some extent at least illusory
• 132: And to erect a new and better standard of common cognition
• 133: What are the real limits of illusory cognition
• 134: In so far as any act of cognition is
• 135: Is bad grouping or carelessly performed synthesis
• 136: Characterize all illusion as partial view
• 137: Must in general be true cognition
• 138: Those of perception and memory
• 139: So far as illusion is useful or only harmless
• 140: It represents the external world as somehow antecedent to
• 141: As they present themselves to the unreflecting intelligence
• 142: Is there any kind of absolutely certain cognition
• 143: Whether sentiments or quasi cognitions
• 144: The associationist passes from genesis to validity
• 145: As one aspect of his problem of cognition
• 146: By the showing of those who affirm them to be illusory
• 147: Illusion distinguished from passive
• 148: Automatic intellectual processes
• 149: The perception of the world as
• 150: In interpretation of sensations
• 151: As element of illusion generally
• 152: Illusions respecting personal identity
• 153: Nervous conditions of hallucination
• 154: Presentation and representation
• 155: Discrimination and classification of
• 156: Illusions by James Sully
• 157: Mental Pathology and Therapeutics London
• 158: In speaking of a fusion of an image and a sensation
• 159: An ingenious article on Optical Illusions of Motion
• 160: On the hypothesis of Young and Helmholtz
• 161: 31 It is brought out by Griesinger loc
• 162: 51 Another side of histrionic illusion
• 163: The liability of children to take images for percepts
• 164: 63 Wundt Physiologische Psychologie
• 165: Die Natur und Entstehung der Traeume
• 166: 98 Physiologische Psychologie
• 167: See Physiologische Psychologie
• 168: Carpenter's Mental Physiology
• 169: 142 To make this rough analysis more complete
• 170: In thus identifying illusion and fallacy