Normative writers criticize the relativist approach and if everything is accepted to be relative, then nothing would have any concrete meaning. On the other hand, those scholars that base their arguments on relativism refuse cosmopolitanism. In other words, they do not accept the universality of some values. Universal law, natural law, universal peace, universal morality, universal human rights are not accepted by them. What Cicero is ultimately saying here and elsewhere is that there is the law of nature, and there is human nature. These are of necessity harmonious with each other (and, ultimately, the same thing) because both reflect the will of a benevolent Supreme Being who creates and governs the universe.