the bulk, texture, and
motion of its insensible parts.
11. How bodies produce ideas in us. The next thing to be
considered is, how bodies produce ideas in us; and that is
manifestly by impulse, the only way which we can conceive bodies to
operate in.
12. By motions, external, and in our organism. If then external
objects be not united to our minds when they produce ideas therein;
and yet we perceive these original qualities in such of them as singly
fall under our senses, it is evident that some motion must be thence
continued by our nerves, or animal spirits, by some parts of our
bodies, to the brains or the seat of sensation, there to produce in
our minds the particular ideas we have of them. And since the
extension, figure, number, and motion of bodies of an observable
bigness, may be perceived at a distance by the sight, it is evident
some singly imperceptible bodies must come from them to the eyes,
and thereby convey to the brain some motion; which produces these
ideas which we have of them in us.
13. How secondary qualities produce their ideas. After the same
manner, that the ideas of these original qualities are produced in us,
we may conceive that the ideas of secondary qualities are also
produced, viz. by the operation of insensible particles on our senses.
For, it being manifest that there are bodies and good store of bodies,
each whereof are so small, that we cannot by any of our senses
discover either their bulk, figure, or motion,- as is evident in the
particles of the air and water, and others extremely smaller than
those; perhaps as much smaller than the particles of air and water, as
the particles of air and water are smaller than peas or
hail-stones;- let us suppose at present that the different motions and
figures, bulk and number, of such particles, affecting the several
organs of our senses, produce in us those different sensations which
we have from the colours and smells of bodies; v.
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