"[A] religious government depends for its existence on the belief of the people - preservation of the faith is the ratio summa status, to which everything else must yield. Therefore not only the civil power enforces the religious law, but the transgressions of the religious must be watched and denounced - therefore espionage and religious detectives, and the use of the peculiar means of information religion provides to give warning to the police. The domain of conscience [is] not distinct therefore from the domain of the State; sins = crimes, and sins against faith, even when private, are acts of treason. Seclusion from the rest of the world necessarily follows, if the rest of the world has not the same religion, or even if it is not governed on the same principles. For liberty is extremely contagious ... Poverty and stationary cultivation, this is to say, in comparison to the rest of the world, retrogression, [are] the price ..." - Lord Acton
The quote is from "Letter on Self-Government and State Absolutism" in the Abbot Gasquet edited Lord Acton and His Circle. And my particular quote of the quote is from AC Grayling's Toward The Light of Liberty.