Christian missionaries argued the Qur’an text itself supports Trinitarian doctrine

Evidence

Ricoldo also developed the argument that Trinitarian faith is implicit in the Qur’an, which speaks of the anima mundi; which speaks with a plural pronoun for God, and which speaks of the Word and of the Spirit of God. … Here he flatly contradicted the actual Islamic attitude; to appeal beyond the Muslim interpretation to the actual text of the Qur’an is not necessarily profitable. — Norman Daniel, Islam and the West, 1014

Categorization

• SEED: Angle: interfaith debate tactics in medieval apologetics — appealing to the other side’s own scripture against its official interpretation, a strategy that predictably fails with the faithful.