Medieval Christian anti-Islamic polemic relied on the Koran’s own text to refute it

Evidence

Riccoldo affirms that reason cannot be used to prove the Trinity or other Christian doctrines, but it can be used to attack Islam. This is of course the standard Dominican strategy, which Ramon Llull bitterly objected to: using reason to denigrate and destroy rather than to build from commonly accepted truths. Since the Koran itself testifies to the authority of the Gospel, Riccoldo continues, Scripture too can be used to disprove the Koran: “one must concentrate on the refutation of such a perfidious law and show that it is not a law of God, and that the Saracens ought to accept the authority of the Gospels and the Old Testaments. We can prove this using the Koran itself, just as Goliath was killed with his own sword.” The strategy he is describing is essentially that of Peter the Venerable: use the Koran to prove the superior authority of the Bible, then use the Bible to attack Muhammad and the Koran and to prove the truth of Christianity. In the more than 150 years since Peter’s Contra sectam, despite the work of scores of Dominican missionaries, despite schooling in Arabic and in Muslim philosophy and theology, the strategy is the same, and the results will be the same: the Dominican missions to Islam are a failure. — John V. Tolan, Saracens, 1263

Categorization

• XREF: Grounds the genealogical claim that the West’s Islamophobic reading strategy is ancient and self-referential — the modern tropes in Anidjar/Aziz derive from this ‘use the Koran against itself’ template.
• DEFINE: Explains the precise rhetorical strategy (Koran testifies to Gospel → use it to attack Muhammad) that defined Latin Christian polemic from Peter the Venerable onward.