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Title: An Essay Towards a New Theory of Vision Author: George Berkeley

 

Release Date: December, 2003 [Etext #4722]

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[This file was first posted on March 7, 2002]

 

Edition: 10

 

Language: English

 

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The Project Gutenberg Etext of An Essay Towards a New Theory of Vision by George Berkeley

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An Essay Towards a New Theory of Vision

by George Berkeley (1685-1753)

 

CONTENTS

 

Sect.

1 Design

2 Distance of itself invisible

3 Remote distance perceived rather by experience than by sense 4 Near distance thought to be perceived by the ANGLE of the OPTIC AXES

5 Difference between this and the former manner of perceiving distance 6 Also by diverging rays

7 This depends not on experience

8 These the common accounts, but not satisfactory 9 Some IDEAS perceived by the mediation of others 10 No IDEA which is not itself perceived, can be the means of perceiving another

11 Distance perceived by means of some other IDEA 12 Those lines and angles mentioned in optics, are not themselves perceived

13 Hence the mind does not perceive distance by lines and angles 14 Also because they have no real existence 15 And because they are insufficient to explain the phenomena 16 The IDEAS that suggest distance are, 1st, the sensation arising from the turn of the eyes

17 Betwixt which and distance there is no necessary connection 18 Scarce room for mistake in this matter 19 No regard had to the angle of the OPTIC AXES

20 Judgment of distance made with both eyes, the result of EXPERIENCE

21 2ndly, Confusedness of appearance

22 This the occasion of those judgments attributed to diverging rays 23 Objection answered

24 What deceives the writers of optics in this matter 25 The cause why one IDEA may suggest another 26 This applied to confusion and distance 27 Thirrdly, the straining of the eye

28 The occasions which suggest distance have in their own nature no relation to it

29 A difficult case proposed by Dr. Barrow as repugnant to all the known theories

30 This case contradicts a received principle in catoptrics 31 It is shown to agree with the principles we have laid down 32 This phenomenon illustrated

33 It confirms the truth of the principle whereby it is explained 34 Vision when distinct, and when confused 35 The different effects of parallel diverging and converging rays 36 How converging and diverging rays come to suggest the same distance 37 A person extreme purblind would judge aright in the forementioned case

38 Lines and angles, why useful in optics 39 The not understanding this, a cause of mistake 40 A query proposed, by Mr. Molyneux in his DIOPTRICS, considered 41 One born blind would not at first have any IDEA of distance by sight 42 This not agreeable to the common principles 43 The proper objects of sight, not without the mind, nor the images of any thing without the mind

44 This more fully explained

45 In what sense we must be understood to see distance and external things

46 Distance, and things placed at a distance, not otherwise perceived by the eye than by the ear

47 The IDEAS of sight more apt to be confounded with the IDEAS of touch than those of hearing are

48 How this comes to pass

49 Strictly speaking, we never see and feel the same thing 50 Objects of SIGHT twofold, mediate and immediate 51 These hard to separate in our thoughts 52 The received accounts of our perceiving magnitude by sight, false 53 Magnitude perceived as immediately as distance 54 Two kinds of sensible extension, neither of which is infinitely divisible

55 The tangible magnitude of an OBJECT steady, the visible not 56 By what means tangible magnitude is perceived by sight 57 This further enlarged on

58 No necessary connection between confusion or faintness of appearance, and small or great magnitude 59 The tangible magnitude of an OBJECT more heeded than the visible, and why

60 An instance of this

61 Men do not measure by visible feet or inches 62 No necessary connection between visible and tangible extension 63 Greater visible magnitude might signify lesser tangible magnitude 64 The judgments we make of magnitude depend altogether on experience 65 Distance and magnitude seen as shame or anger 66 But we are prone to think otherwise, and why 67 The moon seems greater in the horizon than in the meridian 68 The cause of this phenomenon assigned 69 The horizontal moon, why greater at one time than another.

70 The account we have given proved to be true 71 And confirmed by the moon’s appearing greater in a mist 72 Objection answered

73 The way wherein faintness suggests greater magnitude illustrated 74 Appearance of the horizontal moon, why thought difficult to explain 75 Attempts towards the solution of it made by several, but in vain 76 The opinion of Dr. Wallis

77 It is shown to be unsatisfactory

78 How lines and angles may be of use in computing apparent magnitudes 79 One born blind, being made to see, what judgment he would make of magnitude

80 The MINIMUM VISIBLE the same to all creatures 81 Objection answered

82 The eye at all times perceives the same number of visible points 83 Two imperfections in the VISIVE FACULTY

84 Answering to which, we may conceive two perfections 85 In neither of these two ways do microscopes improve the sight 86 The case of microscopical eyes, considered 87 The sight, admirably adapted to the ends of seeing 88 Difficulty concerning erect vision

89 The common way of explaining it

90 The same shown to be false

91 Not distinguishing between IDEAS of sight and touch, cause of mistake in this matter

92 The case of one born blind, proper to be considered 93 Such a one might by touch attain to have IDEAS of UPPER and LOWER

94 Which modes of situation he would attribute only to things tangible 95 He would not at first sight think anything he saw, high or low, erect or inverted

96 This illustrated by an example

97 By what means he would come to denominate visible OBJECTS, high or low, etc.

98 Why he should think those OBJECTS highest, which are painted on the lowest part of his eye, and VICE VERSA 99 How he would perceive by sight, the situation of external objects 100 Our propension to think the contrary, no argument against what has been said

101 Objection

102 Answer

103 An object could not be known at first sight by the colour 104 Nor by the magnitude thereof

105 Nor by the figure

106 In the first act of vision, no tangible thing would be suggested by sight

107 Difficulty proposed concerning number 108 Number of things visible, would not at first sight suggest the like number of things tangible

109 Number the creature of the mind

110 One born blind would not at first sight number visible things as others do

111 The situation of any object determined with respect only to objects of the same sense

112 No distance, great or small, between a visible and tangible thing 113 The not observing this, cause of difficulty in erect vision 114 Which otherwise includes nothing unaccountable 115 What is meant by the picture being inverted 116 Cause of mistake in this matter

117 Images in the eye, not pictures of external objects 118 In what sense they are pictures

119 In this affair we must carefully distinguish between ideas of sight and touch

120 Difficult to explain by words the true Theory of Vision 121 The question, whether there is any IDEA common to sight and touch, stated

122 Abstract extension inquired into

123 It is incomprehensible

124 Abstract extension not the OBJECT of geometry 125 The general IDEA of a triangle, considered 126 Vacuum, or pure space, not common to sight and touch 127 There is no idea, or kind of idea, common to both senses 128 First argument in proof hereof

129 Second argument

130 Visible figure and extension, not distinct IDEAS from colour 131 Third argument

132 Confirmation drawn from Mr. Molyneux’s problem of a sphere and a cube, published by Mr. Locke

133 Which is falsely solved, if the common supposition be true 134 More might be said in proof of our tenet, but this suffices 135 Further reflection on the foregoing problem 136 The same thing doth not affect both sight and touch 137 The same idea of motion not common to sight and touch 138 The way wherein we apprehend motion by sight, easily collected from what hath been said

139 QU. How visible and tangible IDEAS came to have the same name if not of the same kind

140 This accounted for without supposing them of the same kind 141 OBJ. That a tangible square is liker to a visible square than to a visible circle

142 ANS. That a visible square is fitter than a visible circle, to represent a tangible square

143 But it doth not hence follow, that a visible square is like a tangible square

144 Why we are more apt to confound visible with tangible IDEAS, than other signs with the things