In one of the first modern expositions on epistemic modality GH von Wright (1951, 31–32) noted that even though we use the word “possible” frequently in an epistemic sense, there is no unique expression in natural language for an epistemic possibility. What are these possibilities and what sets them apart from other kinds of modalities? 

According to the traditional wisdom a modality (modus) is a manner or a way in which a proposition is true. Hence in addition to being simply true, a proposition may be true in a way that it is known to be true.

In contemporary discussions epistemic modality is determined by a given body of information: If a proposition is epistemically possible, then the proposition is not ruled out by the body of information. If a proposition is epistemically necessary, then the proposition is guaranteed by the body of information. These characterizations raise a spectrum of questions from philosophical to technical. In this tutorial we address some of the questions.

 1. Philosophical background

What is a “body of information”? What is it to “rule out”? What is it to “guarantee”? How epistemic modality relates to logical, metaphysical, and nomological modality? 

2. Hintikka’s (1962) logical framework and its contemporary offspring

Chalmers’ (2012) epistemic two-dimensional semantics: model sets, model systems, epistemic modal operators and quantifiers, epistemic accessibility, knowledge, belief, epistemic possibility. 

3. Problems of Hintikka’s framework

Quantifying into propositional attitude contexts, transworld identification, soundness and completeness of Hintikka’s epistemic logic.    

References

 Bjerring JC 2012 Problems in Epistemic Space, Journal of Philosophical Logic 43/1.

Chalmers D 2004 Epistemic Two-Dimensional Semantics, Philosophical Studies 118.

Chalmers D 2012 Constructing the World, OUP.

Egan A & Weatherson B (eds.) 2011 Epistemic Modality, OUP.

Gendler TS & Hawthorne J (eds.) 2002 Conceivability and Possibility, OUP.

Gendler TS 2010 Intuition, Imagination, and Philosophical Methodology, OUP

Hintikka J 1962 Knowledge and Belief, Cornell University Press, Ithaca.

Huemer M 2007 Epistemic Possibility, Synthese 156.

Jago M 2009 Logical Information and Epistemic Space, Synthese 167.

von Wright GH 1951 An Essay in Modal Logic North-Holland, Amsterdam.

Yablo S 2008 Thoughts, OUP.