Today, through the United Nations and its half century of enactments, an impressive body of human rights doctrine is embodied in international law. This is in sharp contrast to the situation fifty years ago when there was no body of international human rights law. Having come this far legally, why then should one still be concerned with the philosophic foundations of such international human rights law? To philosophize, Plato taught, is to come to know oneself. Others say that the special function of philosophy is to deepen our understanding of truth. Still others see the philosopher as a judge, assessing the varieties of human experience and pronouncing on the claim to knowledge. Yet, still more reasons exist for exploring the philosophic underpinnings of human rights law. First, one’s own attitudes toward the subject of international human rights law are likely to remain obscure unless one understands the philosophies that shape them. Piaget’s statement that “morality is the logic of action” contains a striking insight. Second, if one understands the law addressed, one is more amenable to the authority of the international law of human rights. That trait is particularly valuable for an arena that still lacks formal enforcement mechanisms. Stated another way, one furthers fidelity to human rights law by understanding the moral justifications that underlie that law. Third, understanding the philosophic foundations of the law helps one devise a translation formula that will permit men and women to speak to each other across the gulfs of creed and dogma, a necessary exercise for universal recognition of international law principles. What then is the segment of philosophy examined when delving into human rights? The answer is that human rights are a set of moral principles and their justification lies in the province of moral philosophy. This article explores that field. This article will first address the historical sources of human rights justifications, next survey key modern human rights theories, and then analyze some of the current conflicts in human rights theory. At best, it can only touch on the teachings in a field that is complex, vast, and too often obscure.