This paper explores the analysis of ability, where ability is to be understood in the epistemic sense—in contrast to what might be called a causal sense. There are plenty of cases where an agent is able to perform an action that guarantees a given result even though she does not know which of her actions guarantees that result. Such an agent possesses the causal ability but lacks the epistemic ability. The standard analysis of such epistemic abilities relies on the notion (...) of action types—as opposed to action tokens—and then posits that an agent has the epistemic ability to do something if and only if there is an action type available to her that she knows guarantees it. We show that these action types are not needed: we present a formalism without action types that can simulate analyzes of epistemic ability that rely on action types. Our formalism is a standard epistemic extension of the theory of “seeing to it that”, which arose from a modal tradition in the logic of action. (shrink)

We formulate a Hilbert-style axiomatic system and a tableau calculus for the STIT-based logic of imagination recently proposed in Wansing. Completeness of the axiom system is shown by the method of canonical models; completeness of the tableau system is also shown by using standard methods.

Since Fitch’s proof that not all propositions are knowable, philosophers have analysed the concept of knowability and sought a schema for the knowable propositions. A recent development in dynamic epistemic logic (DEL) has been to read ‘knowable’ as ‘known after an announcement’. Arbitrary Public Announcement Logic (APAL) and Sequential Public Announcement Logic (SPAL) are two DELs that have depicted this reading of knowability. We argue that neither APAL nor SPAL provide a satisfactory and principled schema of the knowable propositions. Instead, (...) we claim that knowability is linked with settledness; stability of truth. We augment SPAL with a settled operator to create a new logic, Dual Sequential Public Announcement Logic (DSPAL). We prove in DSPAL a principled schema of knowability, that all settled propositions are knowable. (shrink)