nsequently make itself or its properties perceivable to the
soul. Whence it plainly follows that it is immediately some contiguous
substance, which, operating on the eye, occasions a perception of
colours: and such is light.

PHIL. Howl is light then a substance?

HYL. . I tell you, Philonous, external light is nothing but a thin fluid
substance, whose minute particles being agitated with a brisk motion, and
in various manners reflected from the different surfaces of outward
objects to the eyes, communicate different motions to the optic nerves;
which, being propagated to the brain, cause therein various impressions;
and these are attended with the sensations of red, blue, yellow, &c.

PHIL. It seems then the light doth no more than shake the optic nerves.

HYL. Nothing else.

PHIL. And consequent to each particular motion of the nerves, the mind
is affected with a sensation, which is some particular colour.

HYL. Right.

PHIL. And these sensations have no existence without the mind.

HYL. They have not.

PHIL. How then do you affirm that colours are in the light; since by
LIGHT you understand a corporeal substance external to the mind?

HYL. Light and colours, as immediately perceived by us, I grant cannot
exist without the mind. But in themselves they are only the motions and
configurations of certain insensible particles of matter.

PHIL. Colours then, in the vulgar sense, or taken for the immediate
objects of sight, cannot agree to any but a perceiving substance.

HYL. That is what I say.

PHIL. Well then, since you give up the point as to those sensible
qualities which are alone thought colours by all mankind beside, you may
hold what you please with regard to those invisible ones of the
philosophers. It is not my business to dispute about THEM; only I would
advise you to bethink yourself, whether, considering the inquiry we are
upon, it be prudent for you to affirm--THE RED AND BLUE WHICH WE SEE ARE
NOT REAL COLOURS, BUT CERTAIN UNKNOWN MOTIONS AND FIGURES WHICH NO MAN
EVER DID OR CAN SEE ARE TRULY SO. Are not these shocking notions, and
are not they subject to as many ridiculous inferences, as those you were
obliged to renounce before in the case of sounds?

HYL. I frankly own, Philonous, that it is in vain to longer. Colours,
sounds, tastes, in a word all those termed SECONDARY QUALITIES, have
certainly no existence without the mind. But by this acknowledgment I
must not be supposed