Natural theology is the part of theology that does not depend upon revelation. During the Middle Ages, natural theology included arguments for the existence and nature of God, for the immortality of the soul, and for the basic principles of morality insofar as they are founded on nature as created by God.

The first flourishing of natural theology was in ancient Greece. Plato's dialogue, the Phaedo, contains a number of weak arguments for the everlastingness of the soul, and Aristotle's Metaphysics contains arguments for a "Prime Mover," which is also the best of all possible beings. In the Christian tradition, medieval theologians, often appealing to Romans 1:18–20, developed the viewed that natural theology could establish the existence of God, which it is logically necessary to do before discussing the things that God had revealed. The first Vatican Council, held from 1869 to 1870, defined as a matter of faith...