In recent years, there have been several books written about dispositions. Barbara Vetter’s Potentiality: From Dispositions to Modality is another, but it is not just another. Vetter’s book stands out as an ambitious, original, and systematic attempt to develop a new account of metaphysical modality in terms of dispositional properties she calls ‘potentialities.’ According to Vetter, saying that something has a disposition, like fragility or flammability, is to say something about what it can do, such as break or burn. Dispositional concepts are members of a broader class of modal concepts, which also includes necessity, possibility, causation, laws, and essence. Vetter’s basic idea is that potentialities are fundamental, and other modal no...