Supposition and realism in Hume

Book 1 of the Treatise is a contribution to logic, one which aims to provide an account of the powers and operations of the human understanding. Hume claims that the operations of the understanding are each a mode of conception. But some passages suggest that there is an operation of the understanding distinct from and irreducible to conception: supposition. Hume’s notion of supposition has been taken to provide a vehicle for realism concerning items of which we have no conception. This chapter argues that the Treatise contains an implicit theory of supposition. That theory is less conducive to realist readings of Hume’s metaphysics than has been thought.