In philosophy of religion, he has lectured and written on the problem of evil, the reasonableness (or lack thereof) of religious faith, and the meanings of religious language. In theology, he has explored the realms of narrative theology, the significance of historical investigations for understanding religious traditions, the ways for theologians to conceive of and account for religious diversity, the practices of Christian discipleship, and, more generally, the practices through which one lives in and lives out faith traditions (including the practice of believing). His work is shaped by a variety of intellectual currents, including speech-act theory, Anglo-American analytical and pragmatic philosophy, hermeneutical theory, critical theory, structuralist and post-structuralist theory, and scholarship on the history and Scriptures of Christianity.
On faculty fellowship (research leave) in AY 2015, Tilley is working on articles and an anticipated book-length manuscript on The Brothers Karamazov. In addition to the Richardson Fellowship, he is lecturing at Chaminade University, Honolulu; Sankt Georgen Graduate School for Philosophy and Theology, Frankfurt/Main, Germany; and St. Norbert's College, De Pere, WI.