Those rights are human rights which, in Professor Gewirth's phrase, “all persons equally have simply insofar as they are human.” His task is to demonstrate that there are human rights, and to demonstrate that such demonstration is necessary to the very existence of these rights. “That human rights exist…is a proposition whose truth depends upon the possibility, in principle, of constructing a body of moral justificatory argument from which that proposition follows as a logical consequence.” As philosophers we should no doubt like to be able to prove the existence of human rights – prove that there are such rights in the event that the fool shall have said in his heart that there are none, even using his folly against him by showing his denial to entail its denial – but it is a bold claim that rights are things whose esse est demonstrari.