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