Seeing all the news about Muslims invading Europe, the killing of Christians in Nigeria, and Islamic efforts to dominate parts of Christian nations, I was led to reflect on St. Thomas Aquinas‘s words in the Summa contra Gentiles, Book I, Chapter 6. He did not mince words when he turned his attention to Muhammad and the origins of Islam. He examines the reasons people should—or should not—believe someone who claims to have been sent by God.
What struck me most about the passage is how directly he approached the question. Unlike many liberal Catholics nowadays, he refused to begin with the assumption that every religious claim deserves equal acceptance. Instead, he asked what kind of evidence ought to accompany a claim of divine revelation.
Aquinas’s criticism of Muhammad touches on three main things: carnal pleasure, violence, and falsehood. These remain uncomfortable subjects, yet they are worth examining because these are the same methods Islam has historically used to expand and dominate, as is clear both then and now.

Carnal Pleasure
On the first point, Aquinas writes that Muhammad “seduced the people by promises of carnal pleasure to which the concupiscence of the flesh goads us,” and that his teaching “gave free rein to carnal pleasure.” For Aquinas, this was significant because the Christian message takes a very different approach to human desire.
Christianity does not promise that following God will satisfy our earthly appetites. Christ calls His disciples to deny themselves, take up their cross, discipline their desires, and follow Him (Luke 9:23). The Christian life therefore involves sacrifice. We are not simply promised whatever the flesh wants; we are called to overcome disordered desires and place them under God’s authority.
Violence
Aquinas also points to the use of force. He writes that Muhammad “said that he was sent in the power of his arms—which are signs not lacking even to robbers and tyrants,” and he speaks of people becoming followers “by the violence of his arms.”
Aquinas contrasts this with the beginnings of Christianity. The Apostles did not preach Christ with armies behind them. The first Christians endured persecution, imprisonment, suffering, and death. Their message was accompanied, according to Christian testimony, by miracles and other signs pointing to the divine mission of Christ and His Apostles.
Falsehood
Aquinas’s strongest words concern what he regarded as falsehood. He writes that Muhammad “perverts almost all the testimonies of the Old and New Testaments by making them into fabrications of his own.” He then argues that preventing followers from reading the earlier Scriptures would keep them from comparing those Scriptures with Muhammad’s claims. Aquinas describes it as a “shrewd decision” to forbid the reading of the Old and New Testaments “lest these books convict him of falsity.”
“No wise men, men trained in things divine and human, believed in him from the beginning. Those who believed in him were brutal men and desert wanderers, utterly ignorant of all divine teaching, through whose numbers Muhammad forced others to become his followers by the violence of his arms.” – Saint Thomas Aquinas on Muhammad

These are severe accusations, but they form part of Aquinas’s larger argument. He believed that claims of divine revelation should be tested against what God had already revealed. Aquinas concludes that Muhammad “did not bring forth any signs produced in a supernatural way, which alone fittingly gives witness to divine inspiration.”
This is why I think Aquinas is worth reading today. Western Christians are living through a time of enormous religious and cultural change. Islam is no longer something most Christians in Europe or North America encounter only in books about distant countries. Muslims are now part of the religious landscape of many traditionally Christian societies.
Christians should avoid the mistake of becoming so afraid of offending others that we stop making distinctions between Christianity and Islam. Christianity makes definite claims about God, Jesus Christ, revelation, Scripture, salvation, and the Church. Islam makes different claims. These differences matter. If Christians continue to lose confidence in their own faith, demographic and cultural changes will only continue to expose a deeper problem. A civilization cannot preserve a Christian identity if its own Christians no longer know or believe Christianity.
The answer is not hatred. It is not panic. It is not hostility toward individual people. The answer is conversion, knowledge, courage, and fidelity to Christ. Catholics need to know Scripture. We need to know the teachings of the Church. We need to teach our children why Christianity is true. We need to support political leaders who continue to resist the Islamization of Christian nations, or it will be too late. We must reject woke ideology, marry and have children, and practice Christianity as it should be practiced. We must also recover a serious life of prayer and the sacraments, and we must be willing to speak the truth about these differences with clarity and charity, even when it is costly.
Most importantly, we must help snatch others from the deception of Islam. As St. Paul warns in Galatians 1:8: “But even if we or an angel from heaven should preach to you a gospel contrary to the one we preached to you, let him be accursed.” Aquinas’s admonition is therefore true: “It is thus clear that those who place any faith in Muhammad’s words believe foolishly.”
Recommended Books
- St. Thomas Aquinas (1975). Summa Contra Gentiles: Book One: God. University of Notre Dame Press
- Robert Spencer. (2013). Not Peace but a Sword: The Great Chasm Between Christianity and Islam. Catholic Answers
- Fr. Samir Khalil Samir (2008). 111 Questions on Islam. Ignatius Press



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