Some authors claim that the talk of moral rights and moral obligations is an old never-ending tale. There are no "moral rights" or "moral obligations" per se ; at least, in the sense that there are also moral rights and moral obligations apart from legal rights and legal obligations. There is no higher ethical authority which may enforce a specific moral demand. Rights and obligations rest on law. According to ethics, one should better say "moral agreements" (for example, Gauthier). The proponents claim that moral agreements do have a similar status to legal rights and legal obligations but stress that no person has an enforceable demand to have her moral rights prevail over others. The suitability is the essential aspect of the metaphysics of rights and obligations. Only the formal constraint establishes rights and obligations within a given society (for example, Hobbes); the informal constraint within a given society - though it may be stronger – is not able to do so. Without a court of first instance there are no rights and obligations. Only by using the legal system is one able to establish specific moral rights and specific moral obligations. Those authors claim that there are no absolute moral rights and moral obligations which are universally valid; moral agreements are always subjective and relative . Hence, there are also no (absolute) moral rights which the fetus (embryo, conceptus, or zygote) may call for. The only solution may be that the survival of the fetus rests on the will of the human beings in a given moral society. According to their view, it is only plausible to argue that an abortion is morally reprehensible if the people in a given society do have a common interest not to abort and make a moral agreement which is enforced by law.