Craig's Kalam and the classical Kalam

The Kalam cosmological argument is one of the best-known arguments for God today, mostly through the work of the Christian philosopher William Lane Craig. His version is short: whatever begins to exist has a cause, the universe began to exist, so the universe has a cause. The argument itself, though, was developed centuries earlier by Muslim theologians, the mutakallimun, such as al-Juwayni, al-Ghazali and Fakhr al-Din al-Razi.

This paper rebuilds the classical argument from its sources and compares the two. Craig's syllogism only concludes that some cause exists. To show that the cause is personal and one, he has to add separate arguments afterwards. The classical version builds these steps into the argument itself: the cause of a universe that began in time must be eternal and necessary; it must act by will, because an eternal cause that acted automatically would have produced an eternal effect; and there can be only one such being, because more than one would make each of them composite and dependent.

The paper also traces how Muslim scholars thought about infinity. Early theologians rejected infinity outright. Later, Imam al-Taftazani distinguished infinities that exist only in the mind, as in mathematics, from infinities of real things in the world, and held that only the second kind is impossible. The authors connect this distinction to Cantor's set theory and to Hilbert's Hotel, the thought experiment Craig himself uses against an actual infinite.