Knowledge and Ockhamist Branching Time

In this paper, we interpret and assess the so-called Fitch’s paradox of knowability by using the Ockhamist semantics for branching-time frames. We argue that the paradox depends in part on the adoption of a strongly idealised notion of knowledge. We emphasize that weaker idealisations are possible. Their nature and the difficulties they meet are highlighted by contraposition with a conception of knowledge as an empirical, almost fully de-idealised notion, such that both the truth-value and the modal status of knowledge ascriptions can change through time and across possible worlds.