METAPHYSICS where capacity can be realized only in a single activity, as with the planets and natural agents, there is no room for a third term between capacity and activity Dispositions are qualities: they fall into one of the nine Aristotelian categories of accident Accidents inhere in substances, and that goes also for dispositions All attributes, Aquinas stresses, are in the last analysis attributes of substances, and all a person’s dispositions are dispositions of a human being What believes, or is generous, or is healthy is, strictly speaking, a man and not his mind or his heart or his body (1a 2ae 50 2) Still, it is not senseless to ask, say, whether skill in writing history is principally a gift of memory or of imagination To ask whether something is a disposition of mind or of body is to ask whether it belongs to a human being qua intelligent being or qua animal of a particular constitution Once again, in attaching dispositions to particular faculties as well as to the substance in which as accidents they ultimately inhere, Aquinas is applying a network of stratiWcation to the original Aristotelian dichotomy of actuality and potentiality The results are sometimes surprising No human activity, he maintains, issues from a purely bodily disposition Bodily activities are either subject to voluntary control or they are not If they are not, then they are natural activities and as such need no disposition to account for them If they are, then the dispositions that account for them must be located primarily in the soul Thus, for Aquinas, the ability to run a marathon is a disposition of the soul no less than the ability to read Hebrew (1ae 2ae 50 1) In general, Aquinas’ treatment of the relation between substance and accident is a natural development of his Aristotelian original But one highly innovative application of the concepts is Aquinas’ account of the Eucharist, the sacrament in which Catholics believed that bread and wine were changed, by the words of the priest at Mass, into Christ’s body and blood The substance of bread, he maintained, gave way to the substance of Christ’s body—that was transubstantiation—and what remained, visible and tangible on the altar, were the mere accidents of bread and wine The shape, colour, and so on of the bread remain without a substance to inhere in (ST 3a 75–7) It is hard to decide whether the concept of accidents inherent in no substance is a coherent one On the one hand, the idea of the Cheshire cat’s grin without the cat seems absurd; on the other hand, the blue of the sky is 197