But we must first begin by distinguishing the two questions.

By things _in our power_, the Stoics meant, things that we could do or acquire, _if we willed_: by things _not in_ our power, they meant, things that we could not do or acquire if we willed.

In both cases, the volition was assumed as a fact: the question, what determined it--or whether it was non-determined, _i.e._ self-determining--was not raised in the abovementioned antithesis.

But it was raised in other discussions between the Stoic theorist Chrysippus, and various opponents.

These opponents denied that volition was determined by motives, and cited the cases of equal conflicting motives (what is known as the ass of Buridan) as proving that the soul includes in itself, and exerts, a special supervenient power of deciding action in one way or the other: a power not determined by any causal antecedent, but self-originating, and belonging to the class of agency that Aristotle recognizes under the denomination of automatic, spontaneous (or essentially irregular and unpredictable).