In common life people recognize many other duties as serious and binding, though of course not necessarily overriding. If philosophers want to call these something else instead of'duties', they must justify their move. The capacity for feelings of pleasure and pain and for the forms oflife of which animals are capable clearly impose duties of compassion and humanity in their case. Words like rights and duties are awkward because they do indeed have narrow senses approximating to the legal, but they also have much wider ones in which they cover the whole moral sphere. Where the realm of right and duty stops, there, to ordinary thinking, begins the realm of the optional. A similar trivialization follows where theorists admit duties of compassion and humanity to non-contractors, but deny duties of justice. The dictum that 'rights and duties are correlative' is quite misleading, because the two words keep different company, and one may be narrowed without affecting the other.