Read this and answer the question. If the question is unanswerable, say "unanswerable".

Another view, advanced by Richard Dawkins, is that the existence of God is an empirical question, on the grounds that "a universe with a god would be a completely different kind of universe from one without, and it would be a scientific difference." Carl Sagan argued that the doctrine of a Creator of the Universe was difficult to prove or disprove and that the only conceivable scientific discovery that could disprove the existence of a Creator would be the discovery that the universe is infinitely old.

What did Richard Dawkins believe was difficult to prove?
unanswerable