This dissertation aims to counteract the natural right of Jonh Finnis with legal positivism of Hans Kelsen, more precisely as the considerations of these authors concerning the discussion about justice, as the reasons put forward by the two theories. The focus of our approach thus turns to the conceptual positivism of Kelsen, connected to the sources of law, where it is not admitted appraising the normative proposition as just or unjust, as well as the neojusnaturalismo of Finnis, who develops a methodology dense around of morality, to show that legal positivism only be able to perform a lucid description of the law, if it serves the tenets laid down in his theory. As a result of this incursion, our goal is also to demonstrate that legal reality requires the undeniable fact that both strands of the right approach at various points, and you may at times claim that the alleged dichotomy is indeed broken.