William Lane Craig on The cosmological argument
Craig defends the Leibnizian cosmological argument alongside the Kalam, arguing the universe requires an explanation for its existence.
In addition to the Kalam, Craig frequently deploys the Leibnizian cosmological argument: everything that exists has an explanation of its existence, either in the necessity of its own nature or in an external cause. The universe exists. Therefore the universe has an explanation — and that explanation, Craig argues, must be a transcendent, necessary being.
Craig sees the Leibnizian version as complementing the Kalam. Where the Kalam argues from the beginning of the universe, the Leibnizian argument works even if the universe is eternal — it asks why there is something rather than nothing, regardless of whether the something had a temporal beginning.
Critics like Graham Oppy argue that the universe might be a brute fact requiring no external explanation. Craig responds that denying the principle of sufficient reason is intellectually costly — it means accepting that things can exist for literally no reason, which he regards as absurd.
“Why does anything exist at all? Leibniz's answer was that the explanation must be found in a being whose existence is metaphysically necessary — a being that could not fail to exist.”