In his greatest rallying cry, the manifesto he entitled the "Act of Union", Lamennais made two arguments which are remarkably salient today. First, ridding a society of theocratic rule does not mean questioning the public presence of the Church. On the contrary, Lamennais contended that freedom of religion must be shored up by freedom of education and association. Second, Catholics could not limit freedom "to their own religious beliefs". He went on: "In each constitutional state, the rights which [Catholics] defend are the public rights of all their fellow-citizens." Lamennais had hit upon what Sturzo calls the "coherence" or reciprocity of rights.

When Lamennais ventured to Rome to persuade the Pope in person, however, his plea for pluralism fell on deaf ears. Gregory XVI thundered against "the erroneous proposition which claims liberty of conscience must be maintained for everyone". Even though "some repeat over and over again with the greatest imprudence that some advantage accrues to religion from it", one should expect nothing more from freedom of opinion than "transformation of minds, corruption of youth, contempt of sacred things and holy law".

Lamennais took that as a "no".

So Rome refused to learn from the experience of losing — in England, Belgium and then Poland — and ignored Lamennais' challenge. Yet it was not long before the Church again suffered strife, again finding herself, in Sturzo's words, "compelled by events to demand these liberties for herself".

In Germany, Bismarck famously initiated the Kulturkampf, or "culture war", in the 1870s. His symbolic exclusion of Catholics from national culture was motivated in part by a view of Catholicism as a foil to modernity, an impediment to progress. Religious orders were banned, seminaries shut down, and the civil service cleansed of Catholics.

But persecution would not be confined to countries where Catholics were a minority. In France, the longer the Third Republic lasted, the more aggressive the policy of laïcité became. In 1901 the government passed a law of association requiring religious orders to gain residency permits in order to exist. Few of these permits were then granted. Becoming prime minister a year later Émile Combes closed 13,000 of France's 16,000 religious schools, boasting of his agenda:

Unlike the Catholic priest anathematising dissent from his bully pulpit — do we [not] impose upon others our rule of conduct and way of thinking . . . All we ask of religion — because we are entitled to do so — is that it keeps within its temples, that it limit its instruction to the faithful, and that it refrain from unwarrantable interference in the civil and political domain.