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. I do not say that the nature of light consists
in very small round globules; nor of whiteness in such a texture of parts as gives a certain rotation to these
globules when it reflects them: for I am not now treating physically of light or colours. But this I think I may say,
that I cannot (and I would be glad any one would make intelligible that he did), conceive how bodies without us
can any ways affect our senses, but by the immediate contact of the sensible bodies themselves, as in tasting and
feeling, or the impulse of some sensible particles coming from them, as in seeing, hearing, and smelling; by the
different impulse of which parts, caused by their different size, figure, and motion, the variety of sensations is
produced in us.
