My guest is Simeon Zahl. He is University Lecturer in Christian Theology at the University of Cambridge. He recently wrote a piece in the Scottish Journal of Theology on the "use" of tradition in theology and what it reveals about the subjective life of the theologian. Building on a close analysis of Martin Luther's distinction between the ‘substance’ of a thing and its ‘use’, the article makes a theological case for the importance of attending not just to what we retrieve from tradition, but also to how and why we retrieve it. Analysis of Luther's distinction suggests (1) that the meaning of theological claims remains unexpectedly fluid until such claims have been located within the ethical drama of ‘use’, and (2) that one of the best ways to get theological traction on the dynamics of ‘use’ is to attend to the affective economies in which theological reasoning is always located. It concludes by drawing attention to specific areas in contemporary ethics where new light can be shed through attention to the dynamics of ‘use’.