In this article I will make a brief reconstruction of Fuller's thinking on the canons of the Inner Morality of Law and in particular about their relationship with the External Morality, the substantive goals of a concrete legal system. This is in order to understand whether the relationship between these two moralities can be meant as a relationship between morally neutral instrumental techniques (legislation) and extra-legal morally oriented purposes, as Hart argued against Fuller; or instead, as Fuller believed, the relationship between the two moralities, or more generally between any means and its end, is of a dynamic type, in virtue of which the end is somehow modified and even defined by the means used for its achievement, and the means itself is to be considered as conceptually inconceivable.