Zachary asked:

A friend of mine claimed to have the proof that God cannot be omnipotent. I said fine. Lay it on me.

He asked the question, "Can God create a stone he himself cannot lift?"

That was several years ago. I've thought about it. I think the question plays not on omnipotence, but
rather our inability to physically comprehend infinity (i.e. picture a universe without end). I know
you've had this question before. But what I'm interested in is the answers given in the past. At the
time the question was posed, this friend of mine expounded upon several answers given by the
Vatican, and if you could dig up a bit of history on this, I would be grateful.

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The supposition that there is such a stone so heavy God cannot lift it, implies a contradiction, since it
implies both that God can and cannot make such a stone.

St. Thomas Aquinas gave the standard answer to this ancient conundrum: It is that God's
omnipotence does not imply that God can do what is logically impossible to do because the "action"
of doing what is logically impossible is really not an action at all, since it describes nothing in just the
way the phrase "four-sided triangle" describes nothing. Mortals are not omnipotent because they
cannot do whatever can be done, such as, for instance, moving a star from one galaxy to another.
God is omnipotent because he can do whatever can be done. even (supposedly) shifting a star, since
doing that does not imply a logical contradiction. But that God cannot do what cannot be done,
namely a logical contradiction, "does not detract from his omnipotence," as Aquinas put it.

Kenneth Stern