hile motion in another direction, as in an
ellipse, should also be a passion or moral reflection: That the shocking
of two globular particles should become a sensation of pain, and that
the meeting of two triangular ones should afford a pleasure. Now as
these different shocks, and variations, and mixtures are the only
changes, of which matter is susceptible, and as these never afford us
any idea of thought or perception, it is concluded to be impossible,
that thought can ever be caused by matter.

Few have been able to withstand the seeming evidence of this argument;
and yet nothing in the world is more easy than to refute it. We need
only reflect on what has been proved at large, that we are never
sensible of any connexion betwixt causes and effects, and that it is
only by our experience of their constant conjunction, we can arrive
at any knowledge of this relation. Now as all objects, which are not
contrary, are susceptible of a constant conjunction, and as no real
objects are contrary [Part III. Sect. 15.]; I have inferred from these
principles, that to consider the matter A PRIORI, any thing may produce
any thing, and that we shall never discover a reason, why any object may
or may not be the cause of any other, however great, or however little
the resemblance may be betwixt them. This evidently destroys the
precedent reasoning concerning the cause of thought or perception. For
though there appear no manner of connexion betwixt motion or thought,
the case is the same with all other causes and effects. Place one body
of a pound weight on one end of a lever, and another body of the same
weight on another end; you will never find in these bodies any principle
of motion dependent on their distances from the center, more than of
thought and perception. If you pretend, therefore, to prove a priori,
that such a position of bodies can never cause thought; because turn it
which way you will, it is nothing but a position of bodies; you must by
the same course of reasoning conclude, that it can never produce motion;
since there is no more apparent connexion in the one case than in the
other. But as this latter conclusion is contrary to evident experience,
and as it is possible we may have a like experience in the operations of
the mind, and may perceive a constant conjunction of thought and motion;
you reason too hastily, when from the mere consideration of the ideas,
you conclude that it is impossible motion can ever produce t