The article examines the doctrine of natural law in 11 Latin commentaries and their Arabic and Byzantine precedents to the Nicomachean Ethics. Our study focuses on Aristotle’s most significant contribution to natural law, i.e., the mutability of what is just by nature. The article systematizes the three strategies used by the commentators to explain this variability of the natural, which we, according to our classification, have termed as “normative,” “ontological” and “hermeneutic.” Subsequently, the article exposes the logic of epikeia, thanks to which the just natural can be adapted to each situation. Finally, we refer to the limits of the mutability of the natural just, both in the permanence of principles given their divine origin and in the intrinsic moral evaluation of certain acts.