  Some interpretations of quantum mechanics use notions of possible states and
possible trajectories. I investigate how this modal approach correlates with
several metaphysical conceptions of a transition from potential to actual
existence. The comparison is based on a discussion in contemporary analytical
metaphysics of modality. I also consider an analogy between Leibniz's theory of
the possibilities striving towards existence, wave mechanics of Schrodinger,
and Feynman path integral.
