 If lives are biological events, it would be useful to know more about what they are, how they are individuated, and what their persistence conditions are. Van Inwagen declines to provide these details (1990, p. 145). He assumes that (the events he calls) lives are familiar enough to us that we can pick them out. But he does make the useful comment that each such event is constituted by certain self-organizing activities in which some molecules engage, and that it is analogous to a parade, which is an event constituted by certain marching-related activities of some people. Having taken the notion of a life for granted, he draws upon it in his account of organisms. On his view (1990, p. 90), some things compose an organism if and only if their activity constitutes a life.