— 311 —
Communication of Motion by Impulse, or by Thought, equally intelligible.       §28. Another Idea we have of Body, is the power of communication
of Motion by impulse; and of our Souls, the power of exciting of Motion
by Thought. These Ideas, the one of Body, the other of our Minds,
every days experience clearly furnishes us with: But if here again we
enquire how this is done, we are equally in the dark. For in the com-
munication of Motion by impulse, wherein as much Motion is lost
to one Body, as is got to the other, which is the ordinariest case, we
can have no other conception, but of the passing of Motion out of
one Body into another; which, I think, is as obscure and uncon-
ceivable, as how our Minds move or stop our Bodies by Thought;
which we every moment find they do. The increase of Motion by
impulse, which is observed or believed sometimes to happen, is yet
harder to be understood. We have by daily experience clear evi-
dence of Motion produced both by impulse, and by thought; but
the manner how, hardly comes within our comprehension; we are
equally at a loss in both. So that however we consider Motion, and
its communication either from Body or Spirit, the Idea which belongs
to Spirit, is at least as clear, as that, that belongs to Body. And if we con-
sider the active power of Moving, or, as I may call it, Motivity, it is
much clearer in Spirit than Body; since two Bodies, placed by one
another at rest, will never afford us the Idea of a power in the one to
move the other, but by a borrowed motion: whereas the Mind, every
day, affords us Ideas of an active power of moving of Bodies; and
therefore it is worth our consideration, whether active power be not
— 312 —
the proper attribute of Spirits, and passive power of Matter. Hence
may be conjectured, that created Spirits are not totally separate
from Matter, because they are both active and passive. Pure Spirit,
viz. God, is only active; pure Matter is only passive; those Beings
that are both active and passive we may judge to partake of both.
But be that as it will, I think, we have as many, and as clear Ideas
belonging to Spirit, as we have belonging to Body, the Substance
of each being equally unknown to us; and the Idea of Thinking in
Spirit, as clear as of Extension in Body; and the communication of
Motion by Thought, which we attribute to Spirit, is as evident, as
that by impulse, which we ascribe to Body. Constant Experience
makes us sensible of both of these, though our narrow Under-
standings can comprehend neither. For when the Mind would look
beyond those original Ideas we have from Sensation or Reflection,
and penetrate into their Causes, and manner of production, we find
still it discovers nothing but its own short-sightedness.
Locke Hum II, 23, §28, pp. 311-312