Challenging the Distinction Between Undercutting and Rebutting Defeaters
When a justified belief is transformed into an unjustified belief, the evidence or mental state that drives that change is referred to as a defeater. Philosophers distinguish between different kinds of defeaters, and one such distinction is commonly made between rebutting and undercutting defeaters. That this distinction is both tenable and important has been orthodoxy since John Pollock (1970; 1999, p. 196) introduced it more than half a century ago Pollock is reported to have seen this distinction “as one of his most important epistemological contributions” (Casullo, 2018, p. 2898). Nobody that I am aware of has doubted its importance, and several authors have recently defended versions of Pollock’s account (Casullo, 2018; McGrath, 2021). In this paper, however, I challenge the orthodoxy. I argue that, taken together, Pollock’s definitions and the assumptions made by subsequent literature imply one of two things: either every defeater is both rebutting and undercutting, which means that there is no material distinction between the two, or else the distinction turns out to be arbitrary, yielding counterintuitive implications and lacking the significance attributed to it.
Epistemic vs Practical Balancing of Reasons
Several authors have noted an apparent contrast between practical and epistemic reasons. As Selim Berker (2018) recently put it, epistemic reasons balance prohibitively whereas practical reasons balance permissively. Berker argues that this contrast lends support to the view that there are no practical reasons for belief. I argue that, contrary to these previous authors, either practical reasons also balance prohibitively, or epistemic reasons never balance prohibitively. Either way, these previous authors were wrong about the contrast and Berker’s argument fails. The discussion reveals new distinctions between types of reason, which, I argue, provide a better explanation for when and why reasons balance prohibitively vs. permissively.