The Kalam cosmological argument in Christianity

The Kalam is, strictly, an Islamic argument — but its twentieth-century afterlife is a Christian story. William Lane Craig's 1979 book The Kalam Cosmological Argument introduced the argument to English-language Christian apologetics, and his tireless debating schedule has made it the most widely rehearsed argument for God in contemporary evangelical discourse. Craig credits al-Ghazali explicitly; the form he defends — 'whatever begins to exist has a cause; the universe began to exist; therefore the universe has a cause' — is substantially Ghazali's.

Craig's innovation is the auxiliary machinery. He supplements the classical philosophical arguments against actual infinites with contemporary cosmology (the Borde-Guth-Vilenkin theorem, which he claims requires any universe with average positive expansion to have a beginning) and with conceptual analysis arguing that the causer of the universe must be personal, immaterial, timeless, and immensely powerful. This fusion of medieval metaphysics, modern cosmology, and analytic philosophy of religion is the calling card of contemporary Christian natural theology.

The argument is contested at every level. Philosophers of physics including Sean Carroll and Alexander Vilenkin himself have pushed back on Craig's cosmological claims; philosophers of religion like Graham Oppy and Wes Morriston have developed detailed critiques of the philosophical premises; even sympathetic Christian philosophers like Keith Ward and Richard Swinburne prefer contingency-based arguments. But within conservative Christian apologetics the Kalam remains dominant, and the argument has become a test case for whether classical natural theology can hold its ground in the face of contemporary physics and analytic critique.