Sagan wrote frequently about religion and the relationship between religion and science, expressing his skepticism about many conventional conceptualizations of God. Sagan once stated, for instance, that "The idea that God is an oversized white male with a flowing beard, who sits in the sky and tallies the fall of every sparrow is ludicrous. But if by 'God,' one means the set of physical laws that govern the universe, then clearly there is such a God. This God is emotionally unsatisfying... it does not make much sense to pray to the law of gravity."[17] Sagan is also widely regarded as a freethinker or skeptic; one of his most famous quotations as seen in Cosmos, was "Extraordinary claims require extraordinary evidence."