First of all, Hitchens' challenge is rigged. You must play by his rules. That means you can only answer with good or noble things that are possible in an atheistic framework. That essentially guarantees the outcome of the challenge in the atheist's favor. Respond with something that a religious person can do which appeals to the existence of God or the supernatural, and you will be laughed out of the room. For instance, an atheist cannot "love the Lord your God with all of your heart, soul, mind, and strength." Jesus said that this was the most important commandment. So, on the Judeo/Christian view, an atheist is incapable of doing the greatest good and most noble thing. Alas, that sort of answer is not allowed. You have to come up with something that is possible for an atheist. See the catch? Thus, the challenge is guaranteed to stump religious people. It essentially says "assuming your religion is false, and the world of physical actions is all the exists, name one moral thing that you can do that an irreligious person can't do."
Second, and more importantly, Hitchen's challenge is actually of little consequence in the debate about God and religion. Nobody is arguing that you have to religious in order to do good. In fact, Christianity teaches that all people are created in the image of God, and are endowed with an inner sense of right and wrong. Hitchen's challenge does not address the real issue: why are some things good and noble? The answer cannot simply be "because we think they are," or "because they benefit us." Such claims lead to moral relativism or consequentialism--things can be good or noble to me, or have outcomes that I deem beneficial, but nothing is really good or noble in itself. In that case, Hitchen's challenge could simply be dismissed. After all, he asked for "one good or noble thing." That is a request for a thing that is objectively good (possessing goodness in and of itself). As it stands, the challenge is akin to saying something like "I challenge you to name an invention that I cannot use unless I believe in inventors." Most of use would immediately realize that as pure nonsense. Of course it is not necessary to believe in inventors in order to use inventions. You can use an iPhone without believing in Steve Jobs. But if no inventors exist, then no inventions would exist. So you would be foolish to make such a claim. The existence of inventions points back to the existence of inventors. Hitchen's is 100% right, it is not necessary to be religious in order to do good or noble things. No one is arguing that. But if God, as a transcendent agent of unchanging moral character, does not exist, then objectively good and noble things also do not exist. That is not a claim that belongs only to Christian apologists. Many of the great atheist thinkers have made the same point (I have written at greater length on the moral argument for God's existence here.) The existence of objectively moral acts points back to the existence of God. Hitchen's challenge simply misses the mark.
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