Colloquium Mathematical Philosophy, Barbara Vetter (Berlin) gives a talk at the MCMP Colloquium (25 April, 2013) titled "How to be a Dispositionalist about Modality". Abstract: In recent years, metaphysicians have become increasingly attracted to the idea that modality is grounded in, or that modal statements are made true by, the dispositions of concrete objects. Some attempts have been made to formulate the view and to respond to objections. Objections typically come in the form of specific counter-examples to the view. I will raise and answer a different and, I believe, more fundamental kind of objection which has so far been neglected: the objection that dispositionalist views of modality get the logic of modality wrong. Possibilities, for instance, are closed under logical implication; but it is far from obvious that dispositions are too. (A glass, by being disposed to break, need not be disposed to be such that I am sitting or not sitting.) To answer the challenge, the metaphysics and logical behaviour of dispositions needs to be spelled out in much more detail. Answering the objection thus provides us with a deeper understanding of dispositionalism about modality.