Argument for the existence of God. According to one version, the universe as a whole is like a machine; machines have intelligent designers; like effects have like causes; therefore, the universe as a whole has an intelligent designer, which is God. The argument was propounded by medieval Christian thinkers, especially St. Thomas Aquinas (Aquinas, Thomas, Saint), and was developed in great detail in the 17th and 18th centuries by writers such as Samuel Clarke (1675–1729) and William Paley (Paley, William S.). It was powerfully criticized by David Hume (Hume, David) in his Dialogues Concerning Natural Religion. Immanuel Kant (Kant, Immanuel) also rejected the argument. In the late 20th century the argument was revived as the doctrine of intelligent design. See also creationism.