The cosmological argument in Christianity

Christianity inherited the cosmological argument from Greek philosophy and refined it across two millennia. Aquinas's Summa Theologiae (1265–1274) presents five distinct arguments from motion, efficient causation, contingency, gradation, and design. The first three are cosmological in structure: each observes a feature of the natural world and argues that it requires an uncaused first mover, a first efficient cause, or a necessary being — which 'all call God.' Aquinas's version is explicitly not a temporal argument; he denied we could philosophically demonstrate that the universe had a beginning, accepting it only on the authority of revelation.

Leibniz reformulated the argument in 1714 around the principle of sufficient reason: every fact must have an explanation either in itself or in something else. Since the universe is contingent (it could have been otherwise), its explanation must lie in a necessarily existing being. This version has been defended in recent decades by Richard Swinburne, Alexander Pruss, and Joshua Rasmussen; its critics, from Hume onward, have challenged the principle of sufficient reason itself, or argued that it applies to parts of the universe but not to the universe as a whole.

The Kalam cosmological argument, associated now with William Lane Craig, is a separate strain — originally developed in medieval Islamic kalam and imported back into Christian apologetics in the late twentieth century. Where the classical Christian arguments rely on contingency or causal chains, the Kalam relies on the claim that the universe began to exist. Contemporary Christian philosophy of religion treats all three strands — Thomist, Leibnizian, and Kalam — as live options. Critics note that even if a cosmological argument succeeds, it gets you to a necessary cause, not to the specifically Christian God; the further argument from the bare first cause to the God of the Trinity remains a separate project.