Steve Ray delivered this talk, “Islam: What Every Infidel Should Know”, at the 2018 Steubenville Defending the Faith Conference.
“On the other hand, those who founded sects committed to erroneous doctrines proceeded in a way that is opposite to this, the point is clear in the case of Muhammad. He seduced the people by promises of carnal pleasure to which the concupiscence of the flesh goads us. His teaching also contained precepts that were in conformity with his promises, and he gave free rein to carnal pleasure. In all this, as is not unexpected, he was obeyed by carnal men. As for proofs of the truth of his doctrine, he brought forward only such as could be grasped by the natural ability of anyone with a very modest wisdom. Indeed, the truths that he taught he mingled with many fables and with doctrines of the greatest falsity. He did not bring forth any signs produced in a supernatural way, which alone fittingly gives witness to divine inspiration; for a visible action that can be only divine reveals an invisibly inspired teacher of truth. On the contrary, Muhammad said that he was sent in the power of his arms—which are signs not lacking even to robbers and tyrants.”
-St. Thomas Aquinas (d. 1274), Theologian and Doctor of the Church. Quoted from his De Rationibus Fidei Contra Saracenos, Graecos, et Armenos and translated from Fr. Damian Fehlner’s Aquinas on Reasons for the Faith: Against the Muslims, Greeks, and Armenians (Franciscans of the Immaculate. 2002.).