This is one of those questions that come from a much different world, where secular is an actual concept, because there is possibility of not only various religions in the same community, but no religion whatsoever, and even laws against allowing religious institutions to control political ones. Peter Laslett had a nice line about the pre-industrial world ( in The World We Have Lost) " Not only zealous priests...not only serious-minded laymen, but also the intellectuals and the publicly responsible looked upon the Christian religion as the explanation of life, and on religious service as its proper end". Someone who had wrong beliefs was threatening to the community, until the gradual spread of toleration, grudgingly at first, in the 18th century. When a madman stood up in a cathedral in early 17th c. Madrid and denied the Virgin Birth, he was not only tortured to death but the entire city went into a frenzy of penance and prayer, as though a vengeful God was going to smash them in retribution. Spain was rather extreme, even for the 17th c., but really few people in Europe or England would dare to publicly deny the existence of God before 1700. It would have been, similarly, the mark of a madman.