Not because the question is too hard to think through, but because if you try to answer it, you have just stepped into a world of nonsense and absurdity. For example, anyone who seriously tried to discuss the question, “How did George Washington like driving with a manual transmission?” is only revealing his or her own ignorance about history.
The same thing is true with the question, “If God can do anything, can God make a stone so heavy that he cannot lift it?” On the surface, the question appears to make the concept of God’s omnipotence ridiculous. If you say “God can do anything,” that implies that God should be able to make an unliftable stone. But if it’s unliftable, then there’s something God can’t do–lift that stone–and so he’s not really omnipotent. On the other hand, if God can’t make an unliftable stone, then there’s something God can’t make–and so he’s not really omnipotent then, either. Either way you answer the question, you have to say God can’t be omnipotent. Ha! Gotcha!
Unfortunately, some people treat this as if it’s a serious philosophical and theological problem. In reality, it’s really just a matter of word tricks and linguistic limitations.
The unliftable rock question reveals the ignorance of the one asking, because it’s a question about . . . nothing.
The question first assumes that God is a being for whom no task (including lifting any stone) is impossible (“if God can do anything). This means that the set “unliftable stones” is empty. Therefore, an “unliftable stone” is a non-entity. Yet the question asks whether such a non-entity can be lifted. Therefore, the question is really asking information about an empty set of objects (unliftable stones). Which is to say that the question is asking information about . . . nothing.
If you try to answer a question that is really asking nothing, you’re going to look really foolish. Instead, demonstrate why the question itself is asking nothing, and therefore deserves no answer.
Here’s a better (a real) question.
Then try this: a legitimate question that leads to more fruitful discussion of God’s omnipotence is: “Is God a being for whom any action is possible?” The answer, of course, is no.
God cannot, for example, sin or kill himself. Does that mean that he is not omnipotent? Of course not, since sinning and killing oneself are not the actions of an all-powerful being. In other words, the inability to perform certain tasks does not necessarily imply lack of power, but, in some cases, the possession of great power.
One way to avoid this linguistic confusion is to speak of God as having limitless power, or as the most powerful possible being, rather than a being who is able to do anything, since the word “anything” may encompass nonsense actions (such as lifting a rock which is unliftable) or actions that are characteristic of impotence (such as dying or sinning).
So there you have it. Don’t let anyone trip you up by the old “can-God-make-a-stone-so-heavy-he-can’t-lift-it” question. Don’t answer it. It’s nonsense.