I work in philosophical logic and specifically on conditionals, belief revision, epistemic logic, logics for artificial intelligence, and logical aspects of metaphysics and epistemology.

My interest in conditionals is longstanding and ongoing. I have published on the logic of even-if, on the relation between conditionals and belief revision, on the connection between conditionals and causation, and, most recently, on the very idea of a semantics for conditionals based on antecedent-relative comparative world similarity. The most interesting unsolved problem about conditionals, in my view, is the issue of how so-called future indicative conditionals (e.g., “If the VCR is left on, the program will not be recorded”) are related semantically both to so-called past indicative conditionals (“If the VCR was left on, the program was not recorded”) and to so-called past subjunctive conditionals (“If the VCR had been left on, the program would not have been recorded”).

My interest in logics for artificial intelligence is similarly both longstanding and ongoing. It began with in the spring of 1986 when I participated in a project on the logic of multiple inheritance with exceptions at Carnegie Mellon University with Rich Thomason, John Horty, and Dave Touretzky. More recently I have become interested in the connection between nonmonotonic reasoning and epistemic coherence (in the sense of BonJour’s coherence theory of justification). In 2003 I published “Nonmonotonic Inconsistency” , which introduces the idea of a defeasible property representing internal conflict of an inductive or evidential nature within a set of statements. In more recent work I argue that the notion of unresolved conflict on which my account of nonmonotonic inconsistency is based helps make sense of holistic epistemic coherence.

Epistemic logic is one of my more recent interests. In my 2001 papers “The Paradox of the Knower without Epistemic Closure” and “A Theorem Concerning Syntactical Treatments of Nonidealized Belief” I show that results similar to Kaplan and Montague’s Knower Paradox and Thomason’s related impossibility result for belief can be obtained without assuming that knowledge or belief is deductively closed.

Over the years I have published on a variety of other topics, too, including the erotetic theory of explanation, probabilistic semantics for modal logic, the epistemic coherence of the whole truth, the simulation of imaging via Popper functions, and David Armstrong’s theory of properties and relations.

I would like to bring together a group of graduate students interested in doing research on conditionals, belief revision, epistemic logic, and/or cumulative reasoning. Prospective graduate students interested in working with me on any of these topics are invited to apply to the Ph.D. Program in Philosophy, the M.A. Program in Philosophy, or the M.S. Program in Artificial Intelligence. Joint enrollment for the M.S. in Artificial Intelligence and the M.A. or Ph.D. in Philosophy is possible and represents a unique opportunity for prospective graduate students interested in logic and its applications.