The Qur’an-endorses-Scripture argument, though logically thin, gripped medieval writers.

Evidence

The different forms of this argument seem to do little more than impose a logical dilemma on Muslims, but it had a very powerful appeal for mediaeval writers. Ricoldo, here heavily indebted to the Spanish schools, copied the Contrarietas, and possibly borrowed from the Cluniacs. — Norman Daniel, Islam and the West, 292