It is customary to dismiss such queries as ‘Can God create a being he cannot control?’ and ‘Can God create a knot he cannot untie?’ with the comment that such questions in fact fail to specify a task for God to perform. The reason given is that omnipotence is included in the idea of God, with the alleged result that such expressions as ‘a being God cannot control’ and ‘a knot God cannot untie’ contain contradictions. J .L. Cowan has argued that this conventional response is mistaken, and subsequently expanded upon this contention in reply to some of its critics. I shall try to show that Cowan's defense of the coherence of expressions like these is mistaken, and with it his conclusion that since an omnipotent God clearly cannot perform such tasks the concept of omnipotence is self-contradictory.

Cowan has no quarrel with one assumption of the customary reply. If the specification of a task is self-contradictory, he agrees that the inability of God to perform it is no blemish on his omnipotence.