Identity Criteria for Metainferential Logics

The emergence of the strict-tolerant logic ST (advocated by Cobreros, Egré, Ripley and van Rooij) and of the hierarchy of increasingly classical logics based upon it (advanced by Barrio, Pailos and Szmuc) sparked many new questions, developments, and debates. One of the central points of discussion is how to identify a logic, or in other words, when two logics can be said to be alternative presentations of one another. Recently, Brian Porter tentatively suggested a new criterion of identity, premised on the intuitive idea that two logics cannot be the same if they admit different applications. In this article, I argue that, although Porter’s criterion is on the right track, it is still unsatisfactory by the author’s own lights. Then, I propose a different criterion which better captures the mentioned intuitive idea.