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 signified] 145 [Several other reasons hereof, assigned] 146 [Reluctancy in rejecting any opinion, no argument of its truth] 147 [Proper objects of vision the language of nature] 148 [In it there is much admirable, and deserving our attention] 149 [Question proposed, concerning the object of geometry] 150 [At first view we are apt to think visible extension the object of geometry] 151 [Visible extension shown not to be the object of geometry] 152 [Words may as well be thought the object of geometry, as visible extension] 153 [It is proposed to inquire, what progress an intelligence that could see, but not feel, might make in geometry] 154 [He cannot understand those parts which relate to solids, and their surfaces, and lines generated by their section] 155 [Nor even the elements of plane geometry] 156 [The proper objects of sight incapable of being managed as geometrical figures] 157 [The opinion of those who hold plane figures to be the immediate objects of sight, considered] 158 [Planes no more the immediate objects of sight, than solids] 159 [Difficult to enter precisely into the thoughts of the above-mentioned intelligence] 160 [The object of geometry, its not being sufficiently understood, cause of difficulty, and useless labour in that science]
AN ESSAY TOWARDS A NEW THEORY OF VISION
1. My design is to show the manner wherein we perceive by sight the distance, magnitude, and situation of OBJECTS. Also to consider the difference there is betwixt the IDEAS of sight and touch, and whether there be any IDEA common to both senses.