Within Lewisian modal realism, de re modality is analyzed in terms of Lewis’ distinctive and controversial counterpart theory. According to counterpart theory, ordinary individuals are not numerically identical or “bilocated” across possible worlds. Instead, possible individuals are worldbound, existing in only one world, and possess their de re modal properties in virtue of bearing counterpart relations to other possible entities. Roughly put, counterpart theory holds that an individual \(a\) is possibly \(F\) if and only if \(a\) has a counterpart that is \(F\), where counterpart relations are relations of qualitative resemblance between possible individuals. So, according to Lewis’ counterpart-theoretic treatment of de re modality, it is true that Obama could have been a doctor if and only if there is some possible individual that appropriately resembles Obama and is a doctor. De re modality is therefore a matter of resemblance relations between parts of possible worlds although the relevant resemblance relations vary from context to context. (Lewis’ views on counterpart theory and counterpart relations change over time, see Lewis (1968, 1986). On counterpart theory, see Graff Fara (2009), Fara and Williamson (2005), and Hazen (1979).)