The sun is capable of producing opposite effects in the terrstial world, for it dissolves ice and dries clay; nevertheless it is an irrational power.
[also] the Philosopher admits in ch. 7 that " every potency is at the same time capable of contradictory states" and declares that this holds good also for active potencies.
[also] according to Aristotle, the rational is not related to both contraries per se, but only it possesses as a habit, whereas the privation of such a habit it can only have per accidents. But an irrational potency is able to have contraries in this fashion, for cold is an accidental cause of heat, and throwing a ball against the wall is the cause of its rebounding. Therefore, the distinction Aristotle makes is not appropriate.
To the contrary in the Ohilosopher's statement in the text [Metaphisics IX q.15).
[How Is the Destinction to Be Understood?]
A]ny active potency whatsoever,be it a power to act in a certain way or an ability to produce something, is such that so long as its nature remained unchanged, it only does what it can do of itself. Frigidity, remaining frigidity, for example, cannot warm or draw heat from itself if it is not this sort of agent. No matter what the circumstances might be, if something associated with it peripherally, for instance, could produce heat in something, it would never be frigidity qua frigidity that would do this.
*frigidity qua frigidity --- phase is ignored, despite of abstract concept of "frigidity"
When we speak of an active potency for opposites, then, be these contradictory or contrary states,it means that with no changes in its nature, either falls equally under the scope of its power. But when such a potency has to do with opposite actions, it meansthat, keeping its unitary character, it suffices to elicit the said actions of itself. And if the action of an active potency is labelled "act" in the sense explained in the third article of the fourth question[i.e., act qua form], then all that has to do with opposite actions or action has to do with opposite acts, but not vice versa. (p.137)