According to an important set of medieval arguments, it is impossible to make a distinction between creation and conservation on the assumption of a beginningless universe. The argument is that, on such an assumption, either God is never causally sufficient for the existence of the universe, or, if He is at one time causally sufficient for the existence of the universe, He is at all times causally sufficient for the universe, and occasionalism is true. I defend the claim that these arguments are successful. Since Christian theology requires a distinction between creation and conservation, arguments in favour of the possible eternity of the world fail.