Self, person, and identity are among the concepts most central to the way humans think about themselves and others. It is often natural in biology to use such concepts; it seems sensible to say, for example, that the job of the immune system is to attack the non-self, but sometimes it attacks the self. But does it make sense to borrow these concepts? Don’t they only pertain to persons, beings with sophisticated minds, and perhaps even souls? I argue that if we focus on the every-day concepts of self and identity, and set aside loftier concepts found in religion, philosophy, and psychology that are applicable, at most, to humans, we can see that self and identity can be sensibly applied widely in biology. Part of a special issue, Ontologi...