John XXIII, Encyclical Letter Peace on Earth: Pacem in Terris (1963).
This encyclical begins by addressing “natural rights” and duties: “The natural rights with which We have been dealing are, however, inseparably connected, in the very person who is their subject, with just as many respective duties; and rights as well as duties find their source, their sustenance and their inviolability in the natural law which grants or enjoins them.” “Therefore, to cite a few examples, the right of every man to life is correlative with the duty to preserve it; his right to a decent standard of living with the duty of living it becomingly; and his right to investigate the truth freely, with the duty of seeking it ever more completely and profoundly.” Pacem in Terris ¶¶28-29.
It then moves on to discuss the nature of the State and its relation to God, from whom it derives its moral authority. It notes that laws passed contrary to the moral order are not binding on citizens (¶51). The major focus, however, is on the relationship between states and their moral duties one to another.
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