Now among the things that become, or among those that although
perpetually existent do not always result in the same actions, it may
be boldly asserted that everything has a cause. We should not admit
(the Stoic contention[99]) that something happens without a cause,
nor accept the (Epicurean[100]) arbitrary convergence of the atoms,
nor believe that any body initiates a movement suddenly and without
determining reason, nor suppose (with Epicurus again[101]) that the
soul undertakes some action by a blind impulse, without any motive.
Thus to suppose that a thing does not belong to itself, that it could
be carried away by involuntary movements, and act without motive, would
be to subject it to the most crushing determinism. The will must be
excited, or the desire awakened by some interior or exterior stimulus.
No determination (is possible) without motive.