What does practice do in theology? How is it used?
Many in theology now write regularly of practice. Practice can be used to describe what people do. It can be the normative result of theological reflection ("Christians should adopt these practices or these should be changed").
But it can also be used in a dodgy way to explain or justify theological claims. As if having abandoned the modern mode of using propositions or clear and distinct claims to legitimate and justify theology, now practice has a dual role. It seems that practice not only is what we do, which I think uncontroversial, but also simultaneously justifies what I do or claim. This is, I think, a natural shift in a post-foundational milieux that has moved from linguistic-turn to narrative-turn to now the turn to practice.
This is strange and unhappy. It has made practices into the philosophers stone for justification.
Stephen P. Turner, The Social Theory of Practice (University of Chicago, 1994) helpfully outlines a critique of this use of practice. He shows how Hume's conventions are a good way forward. Theologically, Johann Georg Hamann's reworking of Hume is valuable here since he holds that it is in fact reason, language, and action that together work in a cross-justificatory system. Convention and custom are not ruled out by Hamann but this does not mean a kind of reductive naturalism like Hume advocates. Instead, it is a sense of multivalent reciprocity between these various human capacities and divine activity.
See Hamann's letters to F H Jacobi of April and May 1784 in ZH VII, 177-8.