In this paper I aim to make sense of our pre‐theoretic intuitions about dispositions by presenting an argument for the identity of a disposition with its putative categorical base. The various possible ontologies for dispositions are outlined. The possibility of an empirical proof of identity is dismissed. Instead an a priori argument for identity is adapted from arguments in the philosophy of mind. I argue that dispositions occupy, by analytic necessity, the same causal roles that categorical bases occupy contingently and (...) that properties with identical causal roles are identical. The validity of the argument depends upon the possibility of overdetermination of disposition manifestations being rejected. ‘Ungrounded dispositions’ are dismissed as not genuine dispositions. Identity conditions for dispositions and categorical bases are outlined. (shrink)