24 But it is not with its own members alone that the Church must come to an amicable arrangement - besides its relations with those within, it has others outside. The Church does not occupy the world all by itself; there are other societies in the world, with which it must necessarily have contact and relations. The rights and duties of the Church towards civil societies must, therefore, be determined, and determined, of course, by its own nature as it has been already described. The rules to be applied in this matter are those which have been laid down for science and faith, though in the latter case the question is one of objects while here we have one of ends . In the same way, then, as faith and science are strangers to each other by reason of the diversity of their objects, Church and State are strangers by reason of the diversity of their ends, that of the Church being spiritual while that of the State is temporal. Formerly it was possible to subordinate the temporal to the spiritual and to speak of some questions as mixed , allowing to the Church the position of queen and mistress in all such, because the Church was then regarded as having been instituted immediately by God as the author of the supernatural order. But his doctrine is today repudiated alike by philosophy and history. The State must, therefore, be separated from the Church, and the Catholic from the citizen. Every Catholic, from the fact that he is also a citizen, has the right and the duty to work for the common good in the way he thinks best, without troubling himself about the authority of the Church, without paying any heed to its wishes, its counsels, its orders - nay, even in spite of its reprimands. To trace out and prescribe for the citizen any line of conduct, on any pretext whatsoever, is to be guilty of an abuse of ecclesiastical authority, against which one is bound to act with all one's might. The principles from which these doctrines spring have been solemnly condemned by our predecessor Pius VI. in his Constitution Auctorem fidei .
Source: Pascendi Dominici Gregis (Vatican.va)