 Notwithstanding the threats posed by certain freely formed groups, the right to exclude is grounded in the belief that, for our associations to be valuable, they must be freely chosen in some measure (Kateb 1998: 36). However, since not all associations operate according to either implicit or explicit declarations of consent, exactly what counts as consent is a difficult thing to assess: How do we know when association is free (Okin 2002)? This problem is exacerbated by the hierarchical form that many associations take. The paradigmatic example of a hierarchical association is that between parents and children. But, hierarchy pervades other connections—between older and younger siblings, employers and employees, states and citizens, and spouses. For some, the fact of acquiescence is sufficient for consent: if a person remains in an association, then she seems to provide evidence that she consents to continued membership. Regardless of how high the cost of leaving an association might be, the person who remains does not exercise her right to exit, which she meaningfully has so long as she is not being physically restrained, and, thus, she is properly describable as free (Kukathas 2003: 113). According to this line of thought, a wife who is psychologically tormented by her spouse, suffering from extreme poverty, and terrified by the outside world as an inhospitable place, remains free to leave her husband.