In Plato’s Sophist (247e), the Eleatic Stranger seems to propose to define being by means of the notion of dynamis. Although some recent papers have claimed that his dynamis-proposal should be taken seriously (at least as an explication of Plato’s concept of being, if not as a definition in the strict sense) it is still far from clear what this claim amounts to – especially in the case of the being of the forms. This paper shows that, regarding forms, a modal and a formal interpretation of the dynamis-proposal is possible. While the latter interpretation is preferable on philosophical and hermeneutical grounds, it seems to conflict with the principle that a form is a being by participating in the form of being. By distinguishing between direct and indirect participation in the form of being, the paper resolves this conflict, concluding that the formal interpretation of the dynamis-proposal can indeed be read as a philosophically attractive holistic explication of Plato’s concept of the being of forms.