Iusnaturalism in front of hume's law: the case of the new natural law theory and its critics

According to authors such as Grisez and Finnis, the classical theory of natural law is immune to the criticism contained in Hume's law argument, because that theory does not pretend to derive ethics from metaphysics, nor practical statements from factual statements. These authors argue that the autonomy of practical reason allows an explanation of the theory of natural law, which does not require any recourse to metaphysics or any other theoretical knowledge of nature. This thesis has been strongly contested by authors linked to neo-Thomism, who deny the validity of the logical rule expressed in Hume's law and, at the same time, affirm that the Thomistic theory of natural law can only be sustained on its metaphysical foundations. This discussion, however, is indicative of the ambiguity with which they have received Hume's law, and of the lack of analysis on the assumptions of such law and on the way in which such assumptions dialogue with the classical tradition of natural law.