The Universal Declaration of Human Rights was proclaimed as a ‘common standard of achievement for all peoples and all nations’ and rests on the claim that persons are ‘endowed with reason and conscience’. The drafters were thus aligned with the claims of the natural law tradition that there are timeless principles of morality – true for all people in all places – and that these principles serve as a guide for lawmakers and a standard to evaluate positive law. Catholic philosopher Jacques Maritain argued that the drafters did not need to agree on the philosophical or metaphysical foundations of morality in order to agree on formulations of practical principles in the language of universal rights. This key insight helped to overcome obstacles to the UDHR and to guide key drafters including Charles Malik. Maritain’s account of natural law in The Rights of Man and Natural Law highlights the notion of jus gentium: commonly agreed principles that are intermediate between the first principles of natural law and positive law. The UDHR can be understood as a successful attempt to formulate jus gentium principles in the aftermath of a war that had seen them disregarded and violated.