Some philosophers, known as “dispositional essentialists”, hold that all fundamental properties are pure dispositions (Ellis 2001; Molnar 2003; Mumford 2004; Bird 2007). On this view, once we have fully described how the electron is disposed to behave, e.g., the disposition to repel other electrons and to attract positrons, or the disposition to exert gravitational attraction on other entities with mass, we have thereby said everything there is to be said about the nature of the electron. Entities on this view are not so much beings as doings.