 A joint activity conception defines the privileged class of common interests as interests that members have in taking part in a complex activity that involves all or most members of the community. Among those who endorse this kind of view are ancient philosophers, such as Plato (Republic) and Aristotle (Politics), secular natural law theorists such as John Finnis (1980), and most natural law theorists in the Catholic tradition. Aspects of the joint activity view are also important in the work of communitarian thinkers such as Charles Taylor (1984) and, to a lesser extent, Michael Sandel (2009). The most important and influential view is Aristotle’s.