"Can God make a weight so heavy that he cannot lift it?"

"Can God make a weight so heavy that he cannot lift it?" asks the unbeliever. He feels he has us cornered. If we say "yes," then God cannot lift it; if we say "no," then God cannot make it [....] Our reply is that God can indeed do all things, but self-contradiction is not a thing. God cannot make a four-sided triangle, because the terms contradict each other and cancel out. A four-sided triangle is meaningless; it is not a thing at all, it is nothing. A weight that an almighty Being cannot lift is as much a contradiction in terms as a four-sided triangle. It too is nothing. And (to give an old text a new emphasis) nothing is impossible to God.

-Frank Sheed, Theology for Beginners