One of the reasons why Roman Catholicism, Calvinism, and Islam have become some of the most widely practiced religions is because of sheer physical dominance. It is undeniable that all 3 religions have taken part in violence for forced conversion. We see this through the torture of those who the church viewed as heretics, burning at the stake, be-headings, and other gruesome forms of violence.
It has been thoroughly documented that Augustine of Hippo was the one who brought this practice into the church in its most aggressive form through his disputes with those he deemed as heretics. The best evidence for this is found in one of his personal letters, which was used to justify the Roman Catholic Inquisition starting in the 16th century.
(Augustine) Augustine's Letters #185 Ch.6: "It is indeed better (as no one ever could deny) that men should be led to worship God by teaching, than that they should be driven to it by fear of punishment or pain; but it does not follow that because the former course produces the better men, therefore those who do not yield to it should be neglected. For many have found advantage (as we have proved, and are daily proving by actual experiment), in being first compelled by fear or pain, so that they might afterwards be influenced by teaching, or might follow out in act what they had already learned in word."
(Augustine) Augustine's Letters #185 Ch.6: "Why, therefore, should not the Church use force in compelling her lost sons to return, if the lost sons compelled others to their destruction? Although even men who have not been compelled, but only led astray, are received by their loving mother with more affection if they are recalled to her bosom through the enforcement of terrible but salutary laws, and are the objects of far more deep congratulation than those whom she had never lost. Is it not a part of the care of the shepherd, when any sheep have left the flock, even though not violently forced away, but led astray by tender words and coaxing blandishments, to bring them back to the fold of his master when he has found them, by the fear or even the pain of the whip, if they show symptoms of resistance; especially since, if they multiply with growing abundance among the fugitive slaves and robbers, he has the more right in that the mark of the master is recognized on them,"
(Augustine) Augustine's Letters #93 Ch.2: "Pharaoh oppressed the people of God by hard bondage; Moses afflicted the same people by severe correction when they were guilty of impiety: their actions were alike; but they were not alike in the motive of regard to the people's welfare—the one being inflated by the lust of power, the other inflamed by love. Jezebel slew prophets, Elijah slew false prophets; (1 Kings 18:4,40) I suppose that the desert of the actors and of the sufferers respectively in the two cases was wholly diverse."
Augustine's beliefs on using force to compel people to return to his church are, however, contradictory to his beliefs in predestination, specifically irresistible grace. If irresistible grace was true, there would be no need for people to share the gospel or do anything with the intention of converting people to his religion. The only way to reconcile these two is to believe that God is using the persecutor to make Himself irresistible to the persecuted, but that statement is even dumber and more profoundly insane. To more fully know how Augustine communicated the doctrine of irresistible grace, see Augustine's Writings on Irresistible Grace.
Influence on Calvinism and Islam
Though I could not find statements where Augustine directly ordered the killing of people with different beliefs, his allusion to those practices was then amplified by both John Calvin and Muhammad. Where Augustine directly stated that people should be compelled with "fear or even the pain of the whip," we see in both Calvinism and Islam the practice of killing people in order to get other people to convert to their religion. We also see that both Calvinism and Islam functioned just like any other religious cult while John Calvin and Muhammad were still alive, having the leader treated like God's gift to mankind and anyone who opposed him would be punished severely, even unto death.
(Commentary on Calvinism) What Love is This? Calvinism's Misrepresentation of God Ch.5 Irresistibly Imposed 'Christianity' Sec.4 Tyranny in Geneva: "Calvin used the civil arm to impose his peculiar doctrines upon the citizens of Geneva and to enforce them. Zweig, who pored over the official records of the City Council for Calvin's day, tells us, "There is hardly a day in the records of the settings of the Town Council, in which we do not find the remark: 'Better consult Master Calvin about this.'" Pike reminds us that Calvin was given a "consultant's chair" in every meeting of the city authorities and "when he was sick the authorities would come to his house for their sessions." Rather than diminishing with time, Calvin's power only grew. John McNeil, a Calvinist, admits that "in Calvin's latter years, and under his influence, the laws of Geneva became more detailed and more stringent.""
(Commentary on Calvinism) What Love is This? Calvinism's Misrepresentation of God Ch.5 Irresistibly Imposed 'Christianity' Sec.5 Don't Cross Dr.Calvin!: "Calvin's power was so great that it was tantamount to treason against the state to oppose him. A citizen named Jacques Gruet was arrested on suspicion of having placed a placard on Calvin's pulpit which read in part, 'Gross hypocrite...! After people have suffered long, they avenge themselves ... Take care that you are not served like M. Verle [who had been killed].' Gruet was tortured twice daily in a manner similar to which Rome, rightly condemned by the reformers for doing so, tortured the victims of her inquisitions who were accused of daring to disagree with her dogmas. The use of torture for extracting 'confessions' was approved by Calvin. After thirty days of severe suffering, Gruet finally confessed-whether truthfully, or in desperation to end the torture, no one knows. On July 16, 1547, 'half dead, he was tied to a stake, his feet were nailed to it, and his head was cut off.'"
(Commentary on Calvinism and Quotes from John Calvin) What Love is This? Calvinism's Misrepresentation of God Ch.5 Irresistibly Imposed 'Christianity' Sec.11 Calvin's Self-Justifications: "He [Calvin] argued that all who oppose God's truth are worse than murderers because murder merely kills the body whereas heresy damns the soul for eternity (was that worse than predestination by God to eternal damnation?) and that God had explicitly instructed Christians to kill heretics and even to smite with the sword every city that abandoned the true faith: 'Whoever shall maintain that wrong is done to heretics and blasphemers in punishing them [with death] makes himself an accomplice in their crime ... it is God who speaks, and it is clear what law He would have kept in the Church even to the end of the world ... so that we spare not kin nor blood of any, and forget all humanity when the matter is to combat for His glory.' ... [next quote from Calvin] 'do not fail to rid the country of those zealous scoundrels who stir up the people to revolt against us. Such monsters should be exterminated, as I have exterminated Michael Servetus the Spaniard.'"
(Islam) Quran 4:65-66 Abdel Haleem Translation: "65 By your Lord, they will not be true believers until they let you decide between them in all matters of dispute, and find no resistance in their souls to your decisions, accepting them totally– – 66 if We had ordered, ‘Lay down your lives’ or ‘Leave your homes,’ they would not have done so, except for a few–– it would have been far better for them and stronger confirmation of their faith, if they had done as they were told,"
(Islam) Quran 24:62 Abdel Haleem Translation: "62 The true believers are those who believe in God and His Messenger, who, when they are gathered with him on a communal matter, do not depart until they have asked his permission–– those who ask your permission [Prophet] are the ones who truly believe in God and His Messenger. When they ask your permission to attend to their private affairs, allow whoever you see fit and ask God to forgive them. God is most forgiving and merciful."
(Islam) Quran 9:4-6 Abdel Haleem Translation: "4 As for those who have honoured the treaty you made with them and who have not supported anyone against you: fulfil your agreement with them to the end of their term. God loves those who are mindful of Him. 5 When the [four] forbidden months are over, wherever you encounter the idolaters, kill them, seize them, besiege them, wait for them at every lookout post; but if they turn [to God], maintain the prayer, and pay the prescribed alms, let them go on their way, for God is most forgiving and merciful. 6 If any one of the idolaters should seek your protection [Prophet], grant it to him so that he may hear the word of God, then take him to a place safe for him, for they are people with no knowledge [of it]."
(Islam) Quran 4:93-94 Abdel Haleem Translation: "93 If anyone kills a believer deliberately, the punishment for him is Hell, and there he will remain: God is angry with him, and rejects him, and has prepared a tremendous torment for him. 94 So, you who believe, be careful when you go to fight in God’s way, and do not say to someone who offers you a greeting of peace, ‘You are not a believer,’ out of desire for the chance gains of this life–– God
has plenty of gains for you. You yourself were in the same position [once], but God was gracious to you, so be careful: God is fully aware of what you do." Just from these few quotes, we can see the similarities between Calvinism and Islam regarding their usage of violence to get people to convert to their religion and then claiming that it was because of God predestinating them to believe.
This post is part of the series The Hard Truth About Calvinism and Islam under The Catholic Origins of Calvinism and Islam