I have argued that theological realism is imprecise about the identity of the God whose mind-independent reality its exponents wish to defend and that it underestimates the problems arising from inadequately distinguishing the God of the philosophers from the triune God of Christian faith. In this chapter we explore the ways in which these difficulties ramify into the heart of theological realism. I shall argue that in their use of analogies with the defence of realism in the philosophy of science, theological realists make a ‘category mistake’. To adapt Gilbert Ryle's definition, they represent the ‘grammar’ of God's existence as if it ‘belonged to one logical type or category’ – in this case, that of science – ‘when actually [it] belong[s] to another’ (Ryle 1963: 17). Theological realists' methodological outlook is controlled more by the philosophy of science than God's self-revelation in Christ. This category mistake has important epistemological and ontological ramifications and suggests that Christians should take leave of theological realism for a more Christologically nuanced understanding of realism orientated by the triune God.

After an introduction to the debate between realist and empiricist perspectives in science and theology, we examine a number of methodological analogies between science and theology presupposed by theological realists. However, it will emerge that from both philosophical and theological perspectives there are significant disanalogies between the two disciplines.