He earned his B.A. from Washington University in St. Louis, his M.A. from the University of Montana, and his Ph.D. from Vanderbilt. His work spans four areas of research: theory of knowledge, ancient philosophy, informal logic and philosophy of religion. In theory of knowledge, he is focused on what it takes to be justified in holding a belief. His work in ancient philosophy has been to investigate the variety of conceptions of knowing in Presocratic philosophy (primarily with Xenophanes) and in Hellenistic philosophy (primarily with the Stoics and Skeptics). His work in informal logic has been focused on epistemic appraisal of arguments and a correlate program for fallacy theory.