The Kalām cosmological argument is a variation of the cosmological argument that argues for the existence of a first cause for the universe, and the existence of a god. Its origins can be traced to medieval Jewish, Christian and Muslim thinkers, but most directly to Islamic theologians of the Kalām tradition. Its historic proponents include Al-Kindi, Saadia Gaon, Al-Ghazali, and St. Bonaventure. William Lane Craig revived interest in the Kalām cosmological argument with his 1979 publication of a book of the same name. The classical argument, as formulated by Al-Ghazali, is as follows: