 Contemporary natural duty theorists differ over the natural duty that provides the basis for political obligation. Christiano grounds his account in a fundamental principle of justice requiring the equal advancement of people’s interests, Wellman in a Samaritan duty of easy rescue, and Stilz in a Kantian duty of respect for others’ freedom-as-independence, understood as a secure sphere of self-determination defined by a person’s rights. These theorists agree, however, that moral agents can discharge their natural duty to others only through submission to the authority of a common legal order. This is so for several reasons: the demands of justice are sometimes underdetermined; its achievement requires the resolution of coordination problems; and most importantly, people reasonably disagree over the demands of justice. Christiano traces this disagreement to what he calls the facts of judgment: diversity in people’s natural talents and cultural surroundings, cognitive biases in their interpretation of people’s interests and the value assigned to their own interests relative to the value assigned to the interests of others, and fallibility in both moral and non-moral judgment. In light of these facts, even those who make a good faith effort to discern what justice requires of them in their interaction with others will fail to reach a consensus. Agents who act on their own, private, judgment of justice will be perceived by others to be acting unjustly. If some are able to unilaterally impose their conception of justice on others, the latter will not enjoy freedom-as-independence (Stilz 2009), or will suffer the violation of their fundamental interests in being at home in the world, in correcting for others’ cognitive biases, and in being treated by one’s fellows as a person with equal moral standing (Christiano 2008). Only submission to a common legal order can provide a solution to this problem of domination and conflict, argue natural duty proponents of political obligation. “There is no way other than general compliance with a single authoritative set of rules to secure peace and protect basic moral rights” (Wellman 2005, p. 45); law “settle[s] for practical purposes what justice consists in by promulgating public rules for the guidance of individual behavior” (Christiano, p. 53); or in Stilz’s Kantian terms, law replaces the unilateral imposition of obligations on others with the omnilateral imposition of obligations on all.