18. The secondary exist in things only as modes of the primary.
A piece of manna of a sensible bulk is able to
produce in us the idea of a round or square figure; and by being removed from one place to another, the idea of
motion. This idea of motion represents it as it really is in manna moving: a circle or square are the same, whether
in idea or existence, in the mind or in the manna. And this, both motion and figure, are really in the manna,
whether we take notice of them or no: this everybody is ready to agree to. Besides, manna, by tie bulk, figure,
texture, and motion of its parts, has a power to produce the sensations of sickness, and sometimes of acute pains
or gripings in us. That these ideas of sickness and pain are not in the manna, but effects of its operations on us,
and are nowhere when we feel them not; this also every one readily agrees to. And yet men are hardly to be
brought to think that sweetness and whiteness are not really in manna; which are but the effects of the operations
of manna, by the motion, size, and figure of its particles, on the eyes and palate: as the pain and sickness caused
by manna are confessedly nothing but the effects of its operations on the stomach and guts, by the size, motion,
and figure of its insensible parts, (for by nothing else can a body operate, as has been proved): as if it could not
operate on the eyes and palate, and thereby produce in the mind particular distinct ideas, which in itself it has not,
as well as we allow it can operate on the guts and stomach, and thereby produce distinct ideas, which in itself it
has not. These ideas, being all effects of the operations of manna on several parts of our bodies, by the size, figure
number, and motion of its parts;--why those produced by the eyes and palate should rather be thought to be really
in the manna, than those produced by the stomach and guts; or why the pain and sickness, ideas that are the effect
of manna, should be thought to be nowhere when they are not felt; and yet the sweetness and whiteness, effects of
the same manna on other parts of the body, by ways equally as unknown, should be thought to exist in the manna,
when they are not seen or tasted, would need some reason to explain.