6 As a consequence, the State, constituted as it is, is clearly bound to act up to the manifold and weighty duties linking it to God, by the public profession of religion. Nature and reason, which command every individual devoutly to worship God in holiness, because we belong to Him and must return to Him, since from Him we came, bind also the civil community by a like law. For, men living together in society are under the power of God no less than individuals are, and society, no less than individuals, owes gratitude to God who gave it being and maintains it and whose ever-bounteous goodness enriches it with countless blessings. Since, then, no one is allowed to be remiss in the service due to God, and since the chief duty of all men is to cling to religion in both its reaching and practice-not such religion as they may have a preference for, but the religion which God enjoins, and which certain and most clear marks show to be the only one true religion -it is a public crime to act as though there were no God. So, too, is it a sin for the State not to have care for religion as a something beyond its scope, or as of no practical benefit; or out of many forms of religion to adopt that one which chimes in with the fancy; for we are bound absolutely to worship God in that way which He has shown to be His will. All who rule, therefore, would hold in honour the holy name of God, and one of their chief duties must be to favour religion, to protect it, to shield it under the credit and sanction of the laws, and neither to organize nor enact any measure that may compromise its safety. This is the bounden duty of rulers to the people over whom they rule. For one and all are we destined by our birth and adoption to enjoy, when this frail and fleeting life is ended, a supreme and final good in heaven, and to the attainment of this every endeavour should be directed. Since, then, upon this depends the full and perfect happiness of mankind, the securing of this end should be of all imaginable interests the most urgent. Hence, civil society, established for the common welfare, should not only safeguard the well-being of the community, but have also at heart the interests of its individual members, in such mode as not in any way to hinder, but in every manner to render as easy as may be, the possession of that highest and unchangeable good for which all should seek. Wherefore, for this purpose, care must especially be taken to preserve unharmed and unimpeded the religion whereof the practice is the link connecting man with God.
Source: Immortale Dei (Vatican.va)