25 The authority of God is passed over in silence, just as if there were no God; or as if He cared nothing for human society; or as if men, whether in their individual capacity or bound together in social relations, owed nothing to God; or as if there could be a government of which the whole origin and power and authority did not reside in God Himself. Thus, as is evident, a State becomes nothing but a multitude which is its own master and ruler. And since the people is declared to contain within itself the spring-head of all rights and of all power, it follows that the State does not consider itself bound by any kind of duty toward God. Moreover, it believes that it is not obliged to make public profession of any religion; or to inquire which of the very many religions is the only one true; or to prefer one religion to all the rest; or to show to any form of religion special favour; but, on the contrary, is bound to grant equal rights to every creed, so that public order may not be disturbed by any particular form of religious belief.
Source: Immortale Dei (Vatican.va)