But we having, by use, been accustomed to perceive
what kind of appearance convex bodies are wont to make in us; what
alterations are made in the reflections of light by the difference
of the sensible figures of bodies;- the judgment presently, by an
habitual custom, alters the appearances into their causes. So that
from that which is truly variety of shadow or colour, collecting the
figure, it makes it pass for a mark of figure, and frames to itself
the perception of a convex figure and an uniform colour; when the idea
we receive from thence is only a plane variously coloured, as is
evident in painting. To which purpose I shall here insert a problem of
that very ingenious and studious promoter of real knowledge, the
learned and worthy Mr. Molyneux, which he was pleased to send me in
a letter some months since; and it is this:- "Suppose a man born
blind, and now adult, and taught by his touch to distinguish between a
cube and a sphere of the same metal, and nighly of the same bigness,
so as to tell, when he felt one and the other, which is the cube,
which the sphere. Suppose then the cube and sphere placed on a
table, and the blind man be made to see: quaere, whether by his sight,
before he touched them, he could now distinguish and tell which is the
globe, which the cube?" To which the acute and judicious proposer
answers, "Not.
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