He is an agnostic atheist. A smart one at that -- and in his honesty cleared up his stance in admitting to his doubt, even as miniscule as it may be. Having been considered the world's foremost atheist for quite some time now (according to the London Telegraph at least) ... I guess he can now be considered the world's foremost agnostic atheist.
http://dictionary.reference.com/browse/atheist
An atheist is one who denies the existence of a deity or of divine beings. An agnostic is one who believes it impossible to know anything about God or about the creation of the universe and refrains from commitment to any religious doctrine.
--- and from Wikipedia: (rather conveniently)
The atheist may however be, and not unfrequently is, an agnostic. There is an agnostic atheism or atheistic agnosticism, and the combination of atheism with agnosticism which may be so named is not an uncommon one. If a man has failed to find any good reason for believing that there is a God, it is perfectly natural and rational that he should not believe that there is a God; and if so, he is an atheist... if he goes farther, and, after an investigation into the nature and reach of human knowledge, ending in the conclusion that the existence of God is incapable of proof, cease to believe in it on the ground that he cannot know it to be true, he is an agnostic and also an atheist – an agnostic-atheist – an atheist because an agnostic... while, then, it is erroneous to identify agnosticism and atheism, it is equally erroneous so to separate them as if the one were exclusive of the other.
--- and of course, if it is on the Internet it must be true. (eyes rolling)