The Logic of Conceivability

Truthmakers Semantics Workshop

Location: Amsterdam Science Park, ILLC, Room F1.15


The Truthmakers Semantics Workshop




9:30-10:00: Welcome and coffee.


10:00-11:00: Peter Hawke (Amsterdam / St Andrews) & Aybüke Özgün (Amsterdam / St Andrews)


Title: Truthmaker semantics for epistemic logic


Abstract: Our purpose is to briefly explore the scope of a truthmaker approach to epistemic logic and the extent to which it can best the Hintikkan approach. We identify three possible targets of analysis for the epistemic logician. Then, we offer a list of candidate epistemic principles and review the arguments that render some controversial. As per its well-known susceptibility to the ‘problem of logical omniscience’, the Hintikka approach validates all of the aforementioned principles, controversial or otherwise. We then lay out a truthmaker framework in the style of Fine (2016, 2017a, forthcoming) and present six different ways of extending this semantics with a (conditional) knowledge operator, drawing on notions of implication and content that are prominent in Fine’s work. We demonstrate that different epistemic logics are thereby generated, bearing on our list of candidate epistemic principles. We offer preliminary observations about the prospects for each logic, relative to (i) a target of analysis for epistemic logic and (ii) philosophical commitments that bear on the candidate principles.


11:00-11:15: Coffee break.


11:15-12:15: Mark Jago (Nottingham)


Title: Disjunctive Parts


Abstract: Kit Fine gives us a theory of content based on truthmaker semantics which distinguishes two kinds of consequence between contents. There is entailment, corresponding to the relationship between disjunct and disjunction, and there is containment, corresponding to the relationship between conjunctions and their conjuncts. Fine associates these with two notions of parthood: disjunctive and conjunctive. Conjunctive parthood is a very useful notion, allowing us to analyse partial content and partial truth. Here, I extend the notion of disjunctive parthood in terms of a structural relation of refinement, which stands to disjunctive parthood much as mereological parthood stands to conjunctive parthood. Philosophically, this relation may be modelled on the determinable-determinate relation, or on a fact-to-fact notion of grounding. I discuss its connection to two other Finean notions: vagueness (understood via precisification) and arbitrary objects. I then investigate what a logic of truthmaking with refinement might look like. I argue that (i) parthood naturally gives rise to a relevant conditional; (ii) refinement underlies a relevant notion of disjunction; and so (iii) truthmaker semantics with refinement is a natural home for relevant logic. 


12:15-14:00: Lunch


14:00-15:00: Janneke van Lith (Utrecht) & Johannes Korbmacher (Utrecht)


Title: Hyperintensional Relevant Alternatives Theory


Abstract: In "Elusive Knowledge" (Lewis 1996), Lewis lays out his Relevant Alternatives Theory (RAT) of knowledge ascriptions. One problem for this theory is that it doesn't work well in hyperintensional contexts, such as knowledge ascription contexts involving mathematical propositions, tautologies, and the like. The failure of RAT to account for such contexts is is odd, to say the least, since as, Schaffer points out, "epistemology is evidently a hyperintensional topic" (Schaffer 2015, 478). In this paper, we develop a hyperintensional version of Lewis's RAT in the framework of exact truthmaker semantics, which has recently been championed by Fine and others (Fine 2017). We will argue that spelling out Lewis' RAT in exact truthmaker semantics leads to a more defensible version of the theory.


15:00-15:15: Coffee break.


15:15-16:15: Maria Aloni (Amsterdam)


Title: Pragmatic enrichments in state-based modal logic


Abstract: In state-based modal logic, formulas are interpreted with respect to a set of possible worlds (a state) in a Kripke model rather than a single world. A state so defined is a less determinate entity than a possible world (comparable to a truthmaker or a situation).
This indeterminate nature makes state-based modal logic particularly suitable to capture a number of phenomena at the semantics-pragmatics interface including the infelicity of epistemic contradictions; free choice permissions and ignorance inference triggered by disjunction and modified numerals.


16:15-17:45: Reception (ILLC Common Room)


18:00: Dinner



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