 Cleanthes and Demea represent the central positions in the eighteenth–century natural religion debate. Cleanthes embodies its dominant, progressive strain, consisting primarily of theologians in the British Royal Society, who were fascinated by probability and the previous century’s impressive successes in experimental natural philosophy. Convinced that the new science gave witness to God’s providence, they rejected traditional a priori proofs, which purported to demonstrate God’s existence with mathematical certainty and without appeal to experience. Instead, they used the order and regularity they found in the universe to construct a probabilistic argument for a divine designer.