21 But a difficulty presents itself. "This Republic," it is said, "is animated by such anti Christian sentiments that honest men, Catholics particularly, could not conscientiously accept it." This, more than anything else, has given rise to dissensions, and in fact aggravated them.... These regrettable differences would have been avoided if the very considerable distinction between constituted power and legislation had been carefully kept in view. In so much does legislation differ from political power and its form, that under a system of government most excellent in form legislation could be detestable; while quite the opposite under a regime most imperfect in form, might be found excellent legislation. It were an easy task to prove this truth, history in hand, but what would be the use? All are convinced of it. And who, better than the Church, is in position to know it - she who has striven to maintain habitual relations with all political governments? Assuredly she, better than any other power, could tell the consolation or sorrow occasioned her by the laws of the various governments by which nations have been ruled from the Roman Empire down to the present.
Source: Au Milieu Des Sollicitudes (Vatican.va)