Medieval Christians assumed Muslims shared common ground on monotheism

Evidence

As William recounts it, in preparation for the debate, he conferred with the Nestorians as to how they should best argue for Christianity. The Nestorians wanted first to debate against the Muslims, but William convinced them that it would be best to argue first against the Buddhists, since the Muslims would side with the Christians in affirming that there is only one God. — John V. Tolan, Saracens, 1135

Categorization

• XREF: Directly relevant to reader’s goal: contradicts the fixed Islam-as-other trope from Aziz/Razack — in this strategic moment Muslims and Christians are presumed natural allies against a genuinely alien paganism.
• SEED: Angle: the genealogy of ‘monotheism’ as a boundary that sometimes united Christians and Muslims against polytheists — a precursor pattern to modern coalitions, pre-dating the hard Islam-West binary.