If neither individual lives nor sets of lives are unified by any significant metaphysical relations, both can be treated as mere collections of experiences.

The success of arguments for this conclusion actually depends on the specific version of reductionism being advanced. After all, there are several possible ethically significant metaphysical units compatible with reductionism, and it turns out that the larger the unit, the less successful the argument will be. As the authors on this topic do, we will focus just on the three possible psychological units: persons, selves, and atoms. If one believes that the only relevant units are atoms (momentar