Augustine in his epistle 50 [185] says: “The king serves God differently as a man and as a king: as a man, he serves Him by living in faith, as a king, by ordering just laws and prohibiting the opposite, and by giving appropriately strong sanctions, just as Hezekiah served God by destroying the groves and temples of the idols; as King Josiah did, by similar acts; as the king of the Ninivites did, by compelling the entire city to appease the Lord; as Darius did, by giving Daniel the authority to destroy the idols; as Nebuchadnezzar did, by a terrible law forbidding everybody who dwelled in his kingdom to blaspheme against God.” And in the same letter he adds: “Who in his right mind would say to kings: in your kingdom do not attend to that which either supports or opposes the Church of your Lord; and who would say to kings: it is not your concern to see who in your kingdom wants to live piously or sacrilegiously? To them it cannot be said, it is not your concern to see who in your kingdom wants to live chastely or unchastely.”
Moreover, in the New Testament, Apocalypse 2, the angel of Pergamos is blamed because he had around him some men who held the doctrine of the Nicolaitanes, and the angel of Thyatira is blamed because he allowed Jezebel to seduce the servants of God. From these things it is gathered that the mixing of Catholics with heretics is harmful to the Church. In Romans 16 Christians are ordered to avoid heretics, in Galatians 5 we read: “I would they were even cut off which trouble you,”167 and in Titus 1: “Wherefore rebuke them sharply, that they may be sound in the faith.”168 Therefore the kings, who are the nursing fathers of the Church, as it is said in Isaiah 49,169 must not allow such mixing.
Second, it is proved with the testimonies of popes and emperors. In his epistle 75 [156] to Leo Emperor, Leo says: “O emperor, you must realize without hesitation that regal authority has been granted to you not only to govern the world, but especially to protect the Church, so that by suppressing the rash attempts of the wicked you might defend that which is well established and restore the true peace in those matters which are perturbed.” Pope Anastasius II in his epistle to Emperor Anastasius says: “I urge on Your Serenity especially this, that when the reasons of the Alexandrines reach your most pious ears, you will drive them back to the Catholic and true faith with your authority, wisdom, and sacred commands.” Gregory says similar things in book 9 [11], epistle 60 [66], to the king of England, and in book 11 [13], epistle 44 [39], to Leontia Augusta, and Agatho as well in his epistle to Constantine IV.
Moreover the pious emperors thought the same, for with the law “Cunctos populos,” title “De summa trinitate et fide Catholica,” Theodosius eradicated completely the freedom of belief that some princes had allowed and he ordered that the teachings of the Roman Pontiff should be believed.170 Ambrose in his Oratio funebris praises Valentinian the younger because he most vigorously resisted the Romans who were asking for the ancient freedom of religion so that they could worship their gods with sacrifices. Similarly Marcian, same title, law “Nemo,” severely prohibits anybody from questioning the matters defined in the Councils of Bishops and from intending to discuss them in public.171
It is true that Constantine the Great at the beginning of his empire allowed everybody freedom of religion, as is clear from the Historia of Eusebius, book 10, chapter 5, but afterward he ordered that the temples of the idols be closed and that only the Christian religion be considered valid, as Optatus reports in his Contra Parmenianum, book 2. Constans and Constantine, his sons, followed in their father’s footsteps, as Augustine reports in epistle 166 [105], and Constantine threatened exile for those who did not assent to the decrees of the Council of Nicaea (Rufinus, bk. 10, chap. 5).
There are three emperors who allowed freedom of religion: Jovian, who was sternly warned by the Council of Antioch not to mix Catholics with heretics, as Socrates writes in book 3, chapter 21. Valens, the Arian emperor, allowed all heretics and pagans the free exercise of their religion, as Theodoretus writes in book 4, chapter 22. Finally, Julian the Apostate, who allowed freedom of religion in the hope of destroying the Christian religion, as Augustine says in epistle 166 or 165 [105]: “Julian, deserter and enemy of Christ, allowed the heretics freedom to be ruined, and then handed over to them the basilicas as temples of devils, thinking that in this way Christianity would disappear from the earth if he broke the unity of the Church from which he had fallen and if he allowed sacrilegious dissensions to develop freely.”
Third, it is proved by reason. First, the temporal and the spiritual authority in the Church are not disconnected and separate things, as two political kingdoms, but are connected so as to form one body; or rather they present themselves as the body and soul in a man, for the spiritual authority is like the soul, and the temporal like the body, as Gregory of Nazianzus teaches in his Oratio ad populum timore perculsum. Therefore the temporal authority must be servant to the spiritual authority and protect and defend it from its enemies, and (as blessed Gregory says, book 2 [3], epistle 61 [65]) the earthly kingdom must attend to the heavenly kingdom. However, the said freedom of religion is destructive for the Church, for the bond of the Church is the profession of one faith, as Paul says in the epistle to the Ephesians 4: “One Lord, one faith, one baptism, etc.”172 Dissension in faith is, therefore, the destruction of the Church. Accordingly, princes must on no account allow this freedom if they want to perform their duty.
Second, when true religion was flourishing among the Jews, the kings could not allow freedom of religion, and much less ought Christian kings to allow it, for the Church must not be arranged any worse than the synagogue was. The antecedent is clear from Deuteronomy 17 where those who do not obey the priest are ordered to be killed, according to the sentence of the civil judge. Similarly in chapter 18 the pseudo-prophets are commanded to be killed, and the same is clear from the examples presented by Augustine in epistle 50 [185] about Hezekiah, Jehoshaphat, Josiah, and other pious kings, who destroyed the groves and temples of the idols and punished severely the idolaters and forced the people to worship the true God. Furthermore, it is not surprising that slightly before Christ’s time various heresies started to be allowed, and in particular that of the Sadducees who denied resurrection, since the synagogue was then coming near its destruction and the Jews had truly no king who could take care of such things, only Herod the Idumaean, and the High Priests could do nothing.
Third, freedom of belief is destructive even for the temporal good of kingdoms and for public peace, as is clear, first, from Gregory, book 4 [5], epistle 32 [20], where he says that the safety of the civil commonwealth depends on the peace of the Church. Second, it is clear by reason, for where faith and obedience to God are preserved, so are faith and obedience to the prince, for faith itself teaches and demands this. Likewise, dissension in faith creates dissensions of spirits and wills, and every kingdom internally divided will perish. The experience of our own times shows the same so clearly that we need not strive to prove it.
Fourth, freedom of belief is destructive for those to whom it is allowed, for it is nothing but the freedom to err, and to err in the matter where error is most dangerous. For the true faith is only one (Ephesians 4, “one Lord, one faith, etc.”); therefore the freedom to move away from that one faith is the freedom to rush into the abyss of errors. Just as it is not beneficial to allow sheep the freedom to wander through the mountains, and it is not beneficial to free the ship from its steering oar and allow it to be carried freely by the wind, so also it is not beneficial to allow the peoples freedom of belief after they have joined the one true faith. The contrary arguments will be disproved in the following question.
Catholics cannot be reconciled with heretics
The third error is that of George Cassander in the book De officio pii viri, where he teaches that princes must find a ground for peace among Catholics, Lutherans, Calvinists, etc. But as long