The teleological argument is an argument for the existence of God or, more generally, that complex functionality in the natural world which looks designed is evidence of an intelligent creator.
Plato and Aristotle, depicted here in The School of Athens, both developed philosophical arguments addressing the universe's apparent order (logos)
The fifth of Thomas Aquinas' proofs of God's existence was based on teleology.
David Hume outlined his criticisms of the teleological argument in his Dialogues Concerning Natural Religion.
Voltaire argued that, at best, the teleological argument could only indicate the existence of a powerful, but not necessarily all-powerful or all-knowing, intelligence.
Natural theology, once also termed physico-theology, is a type of theology that seeks to provide arguments for theological topics based on reason and the discoveries of science, the project of arguing for the existence of God on the basis of observed natural facts, and through natural phenomena viewed as divine, or complexities of nature seen as evidence of a divine plan or Will of God, which includes nature itself.
William Paley, author of Natural Theology