Richard Swinburne

Theism is a far simpler hypothesis, and so a priori more probably true, than naturalism, understood as the hypothesis that the existence of this law-governeduniverse has no explanation. Theism postulates only one entity (God) with very simple properties, whereas naturalism has to postulate either innumerableentities all having the same properties, or one very complicated entity with the power to produce the former. If theism is true, it is moderately probable that God would create humanoid beings and so humanoid bodies; but laws of nature would have to have very special properties if they are to bring about the existencne of humaoid bodies. Given laws of the present form (quantum theory with the Pauli principle and the four forces), the constants of the laws and variables of the boundary conditions of the universe would need to be extremely fine-tuned; and no simpler set of laws would allow the existence of humanoid bodies at all. So the evidence of the existence of humanoid bodies adds further to the probability of theismas against naturalism.

Jeremy Gwiazda made two criticisms of my formulation in terms of Bayes’s theorem of my probabilistic argument for the existence of God. The first criticism depends on his assumption that I claim that the intrinsic probabilities of all propositions depend almost entirely on their simplicity; however, my claim is that that holds only insofar as those propositions are explanatory hypotheses. The second criticism depends on a claim that the intrinsic probabilities of exclusive and exhaustive explanatory hypotheses of a phenomenon must sum to 1; however it is only those probabilities plus the intrinsic probability of the non-occurrence of the phenomenon which must sum to 1