The aim of natural theology is to prove that God exists and to evolve a notion of God by reasoning. This it strives to do in six main arguments: that of general consent (the generality of religious belief bears witness to a law impressed in our nature); the cosmological argument (taking the world as the effect, there must have been a first cause of it); the teleological argument, or argument from design; the ontological argument of St Anselm (which bases belief on the statement that ‘that must exist than which no greater can be conceived’, and has been generally discarded); the argument from humanity's moral sense; and the argument from design in history. Aquinas elaborated the second and third into his five proofs of the existence of God.

In more recent times, there has been considerable debate on the validity of natural theology, particularly between Emil Brunner (1889-1966), who argued that some knowledge of God could be gained from creation, and that this is a necessary part of Christian thought, and Karl Barth, who said that human capacities, especially human reason, are so perverted by sin that they cannot teach anything about God, who can only be known through Jesus Christ and the Word of God.