Fine-tuning, multiple universes and theism

Abstract

The universe appears fine-tuned for life. Bayesian confirmation theory is utilized to examine two competing explanations for this fine-tuning, namely design (theism) and the existence of many universes, in comparison with the ’null’ hypothesis that just one universe exists as a brute fact. Some authors have invoked the so-called ‘inverse gambler’s fallacy’ to argue that the many-universes hypothesis does not explain the fine-tuning of this universe, but flaws in this argument are exposed. Nevertheless, the hypothesis of design, being simpler, is arguably of higher prior probability and, therefore, to be preferred. The hypothesis of the single brute-fact universe is disconfirmed.