Teleology (from the Greek telos meaning "end") is the doctrine that phenomena occur for a purpose. Aristotle argued that to have a complete understanding of anything its "final cause," its purpose in existing, had to be taken into account. The teleological argument for God's existence is that from design.
It was often used, from the seventeenth century on, as a theological argument in favor of pluralism, the argument being that God would not have gone to the trouble of creating uninhabited worlds. Among those to give prominence to teleological reasoning were Jacques Henri Bernadin de Saint-Pierre and John Locke. Opponents of it included Ludwig Büchner.