19. Examples.
Let us consider the red and white colours in porphyry. Hinder light from striking on it, and its
colours vanish; it no longer produces any such ideas in us: upon the return of light it produces these appearances
on us again. Can any one think any real alterations are made in the porphyry by the presence or absence of light;
and that those ideas of whiteness and redness are really in porphyry in. the light, when it is plain it has no colour
in the dark? It has, indeed, such a configuration of particles, both night and day, as are apt, by the rays of light
rebounding from some parts of that hard stone, to produce in us the idea of redness, and from others the idea of
whiteness; but whiteness or redness are not in it at any time, but such a texture that hath the power to produce
such a sensation in us.
