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      §18. 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 the 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 every Body is ready to
agree to. Besides, Manna by the 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 no where 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 it
self it has not, as well as we allow it can operate on the Guts and
Stomach, and thereby produce distinct Ideas, which in it self 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 effects of Manna, should be thought to be no-where, 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
— 139 —
unknown, should be thought to exist in the Manna, when they are
not seen nor tasted, would need some Reason to explain.
Locke Hum II, 8, §18, pp. 138-139