Whilst philosophers and theologians have defended various views on the existence and nature of God, until recently discussion of particular religious doctrines was largely left to theologians. However in his recent book, Was Jesus God?, Richard Swinburne, Emeritus Nolloth Professor of the Philosophy of the Christian Religion in Oxford University, turns his attention to the distinctively Christian account of God and argues that if God exists, then God probably is as Christianity describes him because the main Christian doctrines about God are probably true.

What makes the main Christian doctrines about God probably true? Here Swinburne's argument depends upon his earlier work on confirmation theory and its application to philosophy of religion. According to that, the main Christian doctrines about God should be treated as a hypothesis: Christian theism. And like any other hypothesis, Christian theism needs to be assessed according to whatever evidence there is for it. For Swinburne there are two kinds of such evidence: prior and posterior evidence. Posterior evidence is evidence whose probability depends on a hypothesis’ probable truth or falsity and thus can confirm the hypothesis if it is the sort of thing one would expect were the hypothesis to be true. In the case of Christian theism, this evidence is the historical evidence concerning the life, death and resurrection of Christ. Prior evidence on the other hand, is independent of a hypothesis’ probable truth or falsity. It can affect the hypothesis’ probability, making it more or less probable than it would otherwise be, if it can be shown that the hypothesis fits in with the prior evidence. In the case of Christian theism, Swinburne suggests that the basic features of the universe constitute its prior evidence. Accordingly since Swinburne holds that a hypothesis will be probably true if it is simple, fits in with the prior evidence and leads one to expect posterior evidence not otherwise to be expected (pp. 16, 23) and this is true of Christian theism, then Christian theism will be probably true.

To work out the details Swinburne divides the book into two parts. In the first part after reviewing his earlier work on the existence of God in chapter one, Swinburne tries to show how the main claims of Christianity fit in with the prior evidence for Christian theism. Consequently, if the prior evidence for Christian theism makes the claim that there is a good God moderately probable, then such a God might be expected to exist and act in ways consistent with that. Accordingly Swinburne considers God as triune (chapter two), becoming incarnate (chapter three), atoning for sin (chapter four), teaching humans how to live (chapter five), and offering eternal life to human beings (chapter six) in order to show that these claims are consistent with the claim that there is a good God. The second part of the book considers the posterior evidence that the claims of chapters two to six are true. Here Swinburne discusses Christ's life and death (chapter seven), the resurrection (chapter eight), the Church (chapter ten), the Bible (chapter eleven). Chapter nine offers a provisional conclusion and chapter twelve the main conclusion.

The need to keep Christian theism a simple hypothesis raises difficulties for Swinburne's approach. Take God as triune. On the face of it, the claim that God is a trinity of persons is less simple than the claim that God is one person. That being the case however, since Christian theism is committed to a Trinitarian account of God, on Swinburne's terms it would be less probable than a non-Trinitarian view. To avoid that consequence Swinburne tries to show that God's being triune follows necessarily from God's being good. This gives rise to two problems: why accept Swinburne's inference and even if one does, what about its consequences? As to the consequences: if reason entails that God necessarily is triune, yet scripture only supports the claim that God is triune, then one ends up making reason a source of knowledge of God which is superior to scripture: reason can show that God is necessarily triune, scripture cannot. But even readers sympathetic to Swinburne's project are likely to have reservations about that. As to the inference: why must a perfectly good being have an equal in order to be perfectly loving? Admittedly that might be true of human beings, but no one suggests they are perfectly good. More needs to be done to make that case for a perfect being. Specifically one wonders about Swinburne's confidence that God will act in a recognisably similar way to a human being. Even if one accepts the argumentation however, God the Son and Holy Spirit turn out to be metaphysically necessary i.e. ‘inevitably caused to exist by an ontologically necessary being’ (p. 31). But given that creation for Swinburne is a matter of God knowingly causing something to exist or allowing something else to cause something to exist (p. 12) then the distinction between Son, Spirit on the one hand, and creation on the other, does not seem to be very robust.

Leaving aside issues that arise from the need to keep Christian theism a simple hypothesis, Swinburne is at his best tackling the posterior evidence for Christian theism. The account of Christ's life and death is useful; likewise the way in which Swinburne takes seriously the scriptural and other evidence and marshals it in favour of the resurrection is refreshing. Criticisms notwithstanding, the book is clear, well written and interesting throughout, indeed Christianity is fortunate to have so gifted an advocate as Swinburne. That said however, where many are likely to part company with Swinburne is in his commitment that reason alone is able to access fully the divine mystery.