An Essay Towards a New Theory of Vision | Page 3

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.
2. It is, I think, agreed by all that DISTANCE, of itself and
immediately, cannot be seen. For DISTANCE being a Line directed
end-wise to the eye, it projects only one point in the fund of the eye,
which point remains invariably the same, whether the distance be
longer or shorter.
3. I find it also acknowledged that the estimate we make of the distance

of OBJECTS considerably remote is rather an act of judgment
grounded on EXPERIENCE than of SENSE. For example, when I
perceive a great number of intermediate OBJECTS, such as houses,
fields, rivers, and the like, which I have experienced to take up a
considerable space, I thence form a judgment or conclusion that the
OBJECT I see beyond them is at a great distance. Again, when an
OBJECT appears faint and small, which at a near distance I have
experienced to make a vigorous and large appearance, I instantly
conclude it to be far off: And this, it is evident, is the result of
EXPERIENCE; without which, from the faintness and littleness I
should not have inferred anything concerning the distance of
OBJECTS.
4. But when an OBJECT is placed at so near a distance as that the
interval between the eyes bears any sensible proportion to it, the
opinion of speculative men is that the two OPTIC AXES (the fancy that
we see only with one eye at once being exploded) concurring at