 We can treat the study of defeasible reasoning either (i) as a branch of epistemology (the theory of knowledge), or (ii) as a branch of logic. In the epistemological approach, defeasible reasoning can be studied as a form of inference, that is, as a process by which we add to our stock of knowledge. Alternatively, we could treat defeat as a relation between arguments in a disputational discourse.  In either version, the epistemological approach is concerned with the obtaining, maintaining, and transmission of warrant, with the question of when an inference, starting with justified or warranted beliefs, produces a new belief that is also warranted, given potential defeaters. This approach focuses explicitly on the norms of belief persistence and change.