Abstract:

Reductive approaches to the semantics of de dicto, non-epistemic modality trace back at least to Hume. The task was, and for many still is, to explain our thought and talk of possibility, necessity, and their derivatives in non-modal terms. Hume’s own aim was either to clarify such thought and talk without circularity, or to expose their lack of content altogether. The problem is that, on standard interpretations, Hume’s account of modal thought and talk appears implicitly circular: It requires antecedent appeal to modal thought and talk.

I develop this problem by defending two claims. The first is that, whether Hume’s causal metaphysics is interpreted as reductionist, projectivist, or realist, Hume is taken to explain our modal thought and talk partly by appeal to a “determination of the mind,” or mental determination. This is true of leading reductionist interpretations, for mental determination functions here either as representational content or as a non-representational condition of modal thought and talk. This is true of projectivist interpretations, for mental determination here is either represented as objective or expressed through inferential roles. And it is true of realist interpretations, for here even imprecise or quasi-direct reference to objective causal necessity ultimately defers to a reductionist or projectivist semantics of precise modal thought and talk.

The second claim, which generates the difficulty, is that if a standard interpretation of Hume’s account of mental determination is correct, then mental determination cannot be specified without appeal to modal thought and talk. I survey three dominant interpretations of mental determination in the literature. On one, mental determination is a causal process in the mind; on another, it is a cognitively unavoidable process; on a third, it is an outcome of a mental disposition. I argue that, on each interpretation, mental determination cannot be specified without the use of modal notions. If mental determination is a causal process, it implies a necessary connection between mental states. If it is a cognitively unavoidable process, its specification requires reference to merely possible contrary cognitive processes that fail to occur. And if it is an outcome of a mental disposition, its specification requires appeal both to necessary connections between dispositions and their outcomes, and to what would occur in relevant merely possible circumstances absent defeaters.

If both claims are true, then Hume’s modal semantics is implicitly circular: He explains modal thought and talk partly by appeal to mental determination, yet mental determination itself cannot be specified without appeal to modal thought and talk. I conclude by arguing that this result is best understood not as a failure on Hume’s part, but as a challenge to standard interpretations of his account of mental determination. While these interpretations may avoid circularity by relocating modal commitments to the theorist’s own explanatory activity, doing so presupposes the availability of a strictly non-modal account of mental determination in ordinary human cognition—an account that has yet to be articulated.