Intolerance is natural to man. If, as a matter of fact, men are not always intolerant in practice, it is only because they are prevented by conditions born of reason and wisdom. Respect for the opinion of others supposes a temper of mind which takes years to acquire. It is a questions whether the average man is capable of it. Intolerance regarding religious doctrines especially, with the cruelty that usually accompanies it, has practically been the law of history. From this viewpoint, the temper of mind of the mediæval Christians differed little from that of the pagans of the empire. A Roman of the second or third century considered blasphemy against the gods a crime that deserved the greatest torments; a Christian of the eleventh century felt the same toward the apostates and enemies of the Catholic faith. This is clearly seen from the treatment accorded the first Manicheans who came from Bulgaria, and gained some adherents at Orléans, Montwimer, Soissons, Liège, and Goslar. At once there was a popular uprising against them, which evidenced what may be called the instinctive intolerance of the people. The civil authorities of the day shared this hatred, and proved it either by sending heretics to the stake themselves, or allowing the people to do so. As Lea has said "The practice of burning the heretic alive was thus not the creation of positive law, but arose generally and spontaneously, and its adoption by the legislator was only the recognition of a popular custom."[1] Besides, the sovereign could not brook riotous men who disturbed the established order of his dominions. He was well aware that public tranquillity depended chiefly upon religious principles, which ensured that moral unity desired by every ruler. Pagan antiquity had dreamed of this unity, and its philosophers, interpreting its mind, showed themselves just as intolerant as the theologians of the Middle Ages. [1] Lea, op. cit., vol. i, p. 222.