The fine-tuning argument: the Bayesian version

This paper considers the Bayesian form of the fine-tuning argument as advanced by Richard Swinburne. An expository section aims to identify the precise character of the argument, and three lines of objection are then advanced. The first of these holds that there is an inconsistency in Swinburne’s procedure, the second that his argument has an unacceptable dependence on an objectivist theory of value, the third that his method is powerless to single out traditional theism from a vast number of competitors. In the final section of the paper the fine-tuning argument is considered, not now as self-standing, but as one of a number of theistic arguments taken together and applied in the manner of the final chapter of Swinburne’s The Existence of God. It is argued that points already made also block the way for this line of thought. In an earlier paper (hereafter referred to as FTA) I have discussed what I called ‘the common form’ of the fine-tuning argument. This is the form usually met with; it appeals directly to the sheer improbability of various conditions of life in just the way that the traditional design argument appeals to the improbability of eyes and brains, and concludes similarly that a theistic explanation is called for. At the end of FTA I distinguished the common form of the argument from approaches to the same topic which make an explicit appeal to Bayes’ Theorem. I argued that such approaches involve further questions that go beyond the points made in FTA about the common form. The present paper offers an examination of these further questions arising in the Bayesian fine-tuning argument as it is presented by Richard Swinburne. Swinburne’s exposition, taken as he intends it should be against the background of the Bayesian approach in The Existence of God, constitutes a particularly rich and detailed account of the matter, and one which is well worth the attention of anyone who regards the fine tuning as evidence for theism. Since the present paper is intended to be self-contained, some repetition of points already made in FTA is unavoidable, but this will be kept to a minimum.