When Calvin endorsed the execution of Michael Servetus in 1553, he justified his decision by appeal to (1) the certainty of his own religious faith and (2) the obligation of civil authorities to protect the citizens of Geneva from what he classified as heresy. Théodore de Bèze later defended that rationale in a lengthy Treatise in 1560.
When the Jesuit Cardinal Bellarmine subsequently considered how the Catholic Church should treat heretics, he invoked Calvin’s principle; he quoted Bèze to show that the state must support the eradication of heresy and, if necessary, execute those whom the Roman church classified as heretics (i.e. Calvinists!).
The two Christian churches were symmetrically intolerant of each other. They each appealed to the certainty of their own (incompatible) religious beliefs and to a political theory based on their common reading of the Bible. There followed, in France, decades of religious wars, which petered out only with victory for the majority church at the end of the century.
Two centuries later, a biassed Catholic court in Toulouse sentenced an innocent Huguenot shopkeeper, Jean Calas, to torture on the wheel and public execution. He was accused of murdering his son to prevent him becoming a Catholic, although the son had taken his own life. This monstrous miscarriage of justice prompted Voltaire to write A Treatise on Toleration (1763), in which he pleaded with the civil authorities and the Catholic citizens of France to cease persecuting their Christian fellow citizens. For Voltaire, religious persecution was absurd, and it was inconsistent with the Christian command to love God and one’s neighbour.
The logic of intolerance has been remarkably consistent over many centuries, within different churches and cultures. ...