William Lane Craig on The fine-tuning argument
Craig argues that the fine-tuning of the universe's physical constants is best explained by a cosmic designer.
Craig presents the fine-tuning argument as part of a cumulative case for theism. The physical constants of the universe — the gravitational constant, the strong nuclear force, the cosmological constant — are set to values that permit the existence of complex life. Change any of them by a tiny fraction and the universe produces no stars, no chemistry, and no life.
He considers the three live options: physical necessity (the constants could not have been different), chance, or design. Craig argues that physical necessity is unsupported — there is no known reason the constants must take their observed values. Chance is implausible given the enormous improbability. Design, he concludes, is the best explanation.
Against the multiverse hypothesis favoured by Dawkins and Krauss, Craig argues that it is ad hoc — invoked specifically to avoid the design conclusion, with no independent evidence for its existence. Even if a multiverse exists, Craig contends, it would itself require fine-tuning (a universe-generating mechanism with the right parameters), merely pushing the problem back one level.
“The fine-tuning of the universe is due either to physical necessity, chance, or design. It is not due to physical necessity or chance. Therefore, it is due to design.”