 This plausible observation gives rise to a serious problem. Unless there are constraints on how the objects of choice are individuated, conditions of rationality such as transitivity are empty. A’s choice of X over Y, Y over Z and Z over X does not violate transitivity if “X when the alternative is Y” is not the same object of choice as “X when the alternative is Z”. John Broome (1991) argues that further substantive principles of rationality are required to limit how alternatives are individuated or to require that agents be indifferent between alternatives such as “X when the alternative is Y” and “X when the alternative is Z.”