Lisa Cassell

Epistemic impermissivism is the view that there is never more than one doxastic attitude it is rational to have in response to one's total evidence. Epistemic permissivism is the denial of this claim. The debate between the permissivist and the impermissivist has proceeded, in large part, by way of 'negative' arguments that highlight the unattractiveness of the opposing position. In light of the deadlock that has ensued, this paper has two aims. The first is to introduce the concept of a 'positive' argument for impermissivism. The second is to show that this argument faces a dilemma, one that generalizes the problems that famously arise for formal constraints like the Principle of Indifference. The aim of this paper is to strengthen the argument against the impermissivist by showing that no positive argument for impermissivism is likely to succeed.

This paper considers a problem for Bayesian epistemology and proposes a solution to it. On the traditional Bayesian framework, an agent updates her beliefs by Bayesian conditioning, a rule that tells her how to revise her beliefs whenever she gets evidence that she holds with certainty. In order to extend the framework to a wider range of cases, Jeffrey (1965) proposed a more liberal version of this rule that has Bayesian conditioning as a special case. Jeffrey conditioning is a rule that tells the agent how to revise her beliefs whenever she gets evidence that she holds with any degree of confidence. The problem? While Bayesian conditioning has a foundationalist structure, this foundationalism disappears once we move to Jeffrey conditioning. If Bayesian conditioning is a special case of Jeffrey conditioning, then they should have the same normative structure. The solution? To reinterpret Bayesian updating as a form of diachronic coherentism.

Jonathan Weisberg has argued that Bayesianism’s rigid updating rules make Bayesian updating incompatible with undermining defeat. In this paper, I argue that when we attend to the higher-order beliefs we must ascribe to agents in the kinds of cases Weisberg considers, the problem he raises disappears. Once we acknowledge the importance of higher-order beliefs to the undermining story, we are led to a different understanding of how these cases arise. And on this different understanding of things, the rigid nature of Bayesianism’s updating rules is no obstacle to its accommodating undermining defeat.