The less instructed atheist will ask whether God can make a weight so heavy that He cannot lift it, in the happy belief that, whichever answer we give, we shall admit that there is something God cannot do. But the question is literally meaningless: a weight than an omnipotent Being cannot lift is as complete a contradiction in terms as a four-sided triangle. In either case the words are English, but do not mean anything because they cancel each other out. There is no point in piling together a lot of words, regardless of their meaning, and then asking triumphantly: ‘Can God make that?’ God can do anything, but a contradiction in terms is not a thing at all. It is nothing. God Himself could not make a four-sided triangle or a weight that Almighty power could not lift. They are inconceivable, they are nothing; and nothing–to give a slightly different emphasis to Scripture–is impossible to God.
Frank Sheed, Theology and Sanity