cannot do it when he wills to do so, he does not possess the power to do it. It is therefore impossible for a being to have the power to do what another is doing while that other is doing it; and whatever either produces is within his power.
[Section. Resuming Ibn Rushd’s discussion in Manāhij al-adillah (The Methods of Proof) and Ibn Taymiyyah’s commentary on it]
Section.
Resuming Ibn Rushd’s discussion in Manāhij al-adillah (The Methods of Proof) and Ibn Taymiyyah’s commentary on it
Since, in that case, it is impossible for the other to perform it, and this precludes his having the power to do it, it is impossible for both to have power over the same thing at the same time, or for both to produce the same effect at the same time. Rather, neither can perform the act unless the other leaves him to perform it and refrains from performing it, whether independently or jointly. If either willed to perform it, the other would be unable to do so. Thus, what prevents either from having the power to perform the act independently is the other’s having the power to perform it and actually performing it.
This disproves the existence of two lords in several ways, including the following:
One who is prevented by another is not capable, unlike someone who does not perform an act because he himself does not will it. This does not preclude his having the power to perform the alternative.
If a man has the power to stand and to sit, and chooses one rather than the other, his not doing the other is not due to his inability to do it, but to his not willing it. He does not will to do both simultaneously, because that is intrinsically impossible—not because he lacks power or is incapable of doing it. For what is intrinsically impossible is not a thing whose occurrence can be conceived.
For this reason, those engaged in rational inquiry agree that it is not a thing, and therefore does not fall within His words:
“Indeed, Allah has power over all things.”
[al-Baqarah: 20]
This differs from someone who cannot perform an act because another has performed it. In that case, he has no power to produce the effect brought about by the other, even if he wills to do so.