​The paper reviews the arguments presented by the philosophy of legal positivism to support the separation thesis between morality and law defended by some theorists, in particular Hart and Kelsen. Then it presents the criticism that this philosophy faced from jurists and legal philosophers such as Fuller, Dworkin, and Radbruch, who pleaded for linking morals and law and emphasized the existence of moral assumptions in the concept of the law itself. The paper argues also that legal theory should go beyond the traditional separation between theories of natural law and theories of legal positivism and between legal obligations and moral duties so that it can give the principle of the rule of law a central role in protecting human rights and achieving justice in contexts of injustice, tyranny, violence, mass killings and forced displacement that abound in modern human history in many countries of the world.