There was no technological barrier to prevent the ancient world from matching the achievements of Kepler in astronomy, Galileo in mechanics or Pascal on the atmosphere. One reason why they did not do so may be related to the metaphysical assumptions that the Greeks brought to natural philosophy. This talk contrasts Greek thought about creation in their philosophical and mythical texts with Christian theology in both late antiquity and the Middle Ages. I will suggest that, in general, creation was not a religious question to the Greeks and that this left considerable space for the various philosophical schools to provide their own account of where the world came from and how it was constructed. In contrast, for Christians, creation was of critical theological importance. This meant that Christians, in the Latin tradition at least, shared certain underlying assumptions about nature which derived from the work of theologians from Augustine onwards. I argue that these assumptions turned out to be particularly conducive to the development of natural philosophy into modern science. That they were shared and were not just a single product in the marketplace of ideas was also critical. The Greeks suffered from a surfeit of metaphysical systems with no way to test which ones might lead them to accurate theories about the natural world.