While preparing my suitcase for Padua, I took care to put my favorite cds in a secured spot since they could have broken along the way. Which (non-mental) fact, if any, could possibly justify my action – i.e. what, if anything, makes it the case that my cds could have broken? The paper explores the nature of possibility. The three theories most widely endorsed thus far – fictionism, actualism, and modal realism – are introduced, with a particular attention to their (...) unpalatable ontological consequences. In order to avoid such consequences, a fourth theory is put forward. The goal of the theory is to explain the nature of possibility on the basis of actual (vs possible) entities while, at the same time, providing a non-circular interpretation of the meaning of our modal talk on the basis of such actual entities. Dispositions are meant to be the ontological ground of the theory. They play the role of possibilia – i.e. the entities on the basis of which we interpret modal assertions. A characterization of the sort of dispositions needed for grounding the theory is given. Finally follow some remarks on the effects of the theory upon the extension of the domain of possibilia. (shrink)