85 But one of the principal imperatives of the common good is the recognition of the moral order and the unfailing observance of its precepts. "A firmly established order between political communities must be founded on the unshakable and unmoving rock of the moral law, that law which is revealed in the order of nature by the Creator Himself, and engraved indelibly on men's hearts . . . Its principles are beacon lights to guide the policies of men and nations. They are also warning lights—providential signs—which men must heed if their laborious efforts to establish a new order are not to encounter perilous storms and shipwreck." (54)
Source: Pacem in Terris (Vatican.va)