e. numbers and figures,
can be set down by visible and lasting marks, wherein the ideas
under consideration are perfectly determined; which for the most
part they are not, where they are marked only by names and words.
11. Modes of qualities not demonstrable like modes of quantity.
But in other simple ideas, whose modes and differences are made and
counted by degrees, and not quantity, we have not so nice and accurate
a distinction of their differences as to perceive, or find ways to
measure, their just equality, or the least differences. For those
other simple ideas, being appearances of sensations produced in us, by
the size, figure, number, and motion of minute corpuscles singly
insensible; their different degrees also depend upon the variation
of some or of all those causes: which, since it cannot be observed
by us, in particles of matter whereof each is too subtile to be
perceived, it is impossible for us to have any exact measures of the
different degrees of these simple ideas. For, supposing the
sensation or idea we name whiteness be produced in us by a certain
number of globules, which, having a verticity about their own centres,
strike upon the retina of the eye, with a certain degree of
rotation, as well as progressive swiftness; it will hence easily
follow, that the more the superficial parts of any body are so ordered
as to reflect the greater number of globules of light, and to give
them the proper rotation, which is fit to produce this sensation of
white in us, the more white will that body appear, that from an
equal space sends to the retina the greater number of such corpuscles,
with that peculiar sort of motion.
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