The Logic and Metaphysics Workshop will meet on October 23rd from 4:15-6:15 (NY time) in-person at the Graduate Center (Room 4419) for a talk by Melissa Fusco (Columbia).

Title: Diachronic reasoning with conditionals

Abstract: I will discuss a hybrid decision theory, coinciding sometimes with (traditional) Evidential Decision Theory, but usually with (traditional) Causal Decision Theory, which is inspired by recent work on unified and fully compositional approaches to the probabilities of conditionals. The hybrid theory features a few other loci of interest: the partitionality of acts A ∈ {A} fails, and close attention is paid to how one might (dis)confirm chance hypotheses under the umbrella of the Principal Principle. On this theory, the probabilities of conditionals play a role in underwriting a theory of imaging that follows Skyrms’s Thesis (Skyrms, 1981, 1984). Moreover, the credences it is epistemically rational to assign to these conditionals guides updating on one’s own acts. This implies some departures from Conditionalization, which I defend on epistemological grounds.

The Logic and Metaphysics Workshop will meet on October 16th from 4:15-6:15 (NY time) in-person at the Graduate Center (Room 4419) for a talk by Yale Weiss (CUNY).

Title: Maximal deontic logic

Abstract: The worlds accessible from a given world in Kripke models for deontic logic are often informally glossed as ideal or perfect worlds (at least, relative to the base world). Taking that language seriously, a straightforward but nonstandard semantic implementation using models containing maximally good worlds yields a deontic logic, MD, considerably stronger than that which most logicians would advocate for. In this talk, I examine this logic, its philosophical significance, and its technical properties, as well as those of the logics in its vicinity. The principal technical result is a proof that MD is pretabular (it has no finite characteristic matrix but all of its proper normal extensions do). Along the way, I also characterize all normal extensions of the quirky deontic logic D4H, prove that they are all decidable, and show that D4H has exactly two pretabular normal extensions.

The Logic and Metaphysics Workshop will meet on October 2nd from 4:15-6:15 (NY time) in-person at the Graduate Center (Room 4419) for a talk by Brett Topey (Salzburg).

Title: Whence admissibility constraints? From inferentialism to tolerance

Abstract: Prior’s invented connective ‘tonk’ is sometimes taken to reveal a problem for certain inferentialist approaches to metasemantics: according to such approaches, the truth-theoretic features of our expressions are fully determined by the rules of inference we’re disposed to follow, but admitting the ‘tonk’ rules into a language would lead to intuitively absurd results. Inferentialists tend to insist that they can avoid these results: there are constraints on what sets of inference rules can be admitted into a language, the story goes, and the rules governing disruptive expressions like ‘tonk’ are defective and so illegitimate. I argue, though, that from an inferentialist perspective, there’s no genuine sense in which rules like the ‘tonk’ rules are defective; those who endorse the relevant sort of inferentialism turn out to be committed to Carnap’s principle of tolerance. I then sketch an argument to the effect that this, despite appearances, isn’t a problem for inferentialism.

The Logic and Metaphysics Workshop will meet on September 18th from 4:15-6:15 (NY time) in-person at the Graduate Center (Room 4419) for a talk by Will Nava (NYU).

Title: Non-classicality all the way up

Abstract: Nearly all non-classical logics that have been studied admit of classical reasoning aboutthem. For example, in the logic K3, A or not-A is not a valid schema. However, ‘A or not-A’ is K3-valid or not K3-valid—this is, in some sense, a valid claim. In this talk, I introduce a simple framework for thinking about the logic of a given logic. This allows for a measure of the non-classicality of a logic—one on which almost all familiar non-classical logics are of the lowest grade of non-classicality. I’ll then discuss some strategies for generating and theorizing logics of higher grades of non-classicality, as well as some motivation for taking these logics seriously.