"Plato," writes Gaston Boissier, "in his ideal Republic, denies toleration to the impious, i.e., to those who did not accept the State religion. Even if they remained quiet and peaceful, and carried on no propaganda, they seemed to him dangerous by the bad example they gave. He condemned them to be shut up in a house where they might learn wisdom (_sophronisteria_)--by this pleasant euphemism he meant a prison--and for five years they were to listen to a discourse every day. The impious who caused disturbance and tried to corrupt others were to be imprisoned for life in a terrible dungeon, and after death were to be denied burial."[1] Apart from the stake, was not this the Inquisition to the life? In countries where religion and patriotism went hand in hand, we can readily conceive this intolerance. Sovereigns were naturally inclined to believe that those who interfered with the public worship unsettled the State, and their conviction became all the stronger when the State received from heaven a sort of special investiture. This was the case with the Christian empire. Constantine, towards the end of his career, thought himself ordained by God, "a bishop in externals,"[1] and his successors strove to keep intact the deposit of faith. "The first care of the imperial majesty," said one of them, "is to protect the true religion, for with its worship is connected the prosperity of human undertakings."[2] Thus some of their laws were passed in view of strengthening the canon law. They mounted guard about the Church, with sword in hand, ready to use it in her defence. [1] Eusebius, _Vita Constantini_, lib. iv, cap. xxiv. [2] Theodosius II, _Novellæ_, tit. iii (438). The Middle Ages inherited these views. Religious unity was then attained throughout Europe. Any attempt to break it was an attack at once upon the Church and the Empire. "The enemies of the Cross of Christ and those who deny the Christian faith," says Pedro II, of Aragon, "are also our enemies, and the public enemies of our kingdom; they must be treated as such."[1] It was in virtue of the same principle that Frederic II punished heretics as criminals according to the common law; _ut crimina publica_. He speaks of the "Ecclesiastical peace" as of old the emperors spoke of the "Roman peace." As Emperor, he considered it his duty "to preserve and to maintain it," and woe betide the one who dared disturb it. Feeling himself invested with both human and divine authority, he enacted the severest laws possible against heresy. What therefore might have remained merely a threatening theory became a terrible reality. The laws of 1224, 1231, 1238, and 1239 prove that both princes and people considered the stake a fitting penalty for heresy. [3] Law of 1197, in De Marca, _Marca Hispanica_, col. 1384.