Islam’s monotheism made medieval Christians doubt whether Muslims were infidels at all.

Evidence

The apologists were fighting an uphill battle, as most Cordovan Christians resented the trouble wrought by the martyrs, whom they deemed fanatics; were they not “killed by men who venerated both God and a law”? This, for Eulogius and Alvarus, is fuzzy theological thinking; there can be no truth (or half-truth) outside of Christianity. If Christian Cordovans entertain such dangerous errors, the fault lies with the bishops who fail to guide their flock. — John V. Tolan, Saracens, 514

Categorization

• XREF: Evidences the reader’s existing vault claim that Islamic monotheism blurred the Christian infidel boundary—contemporaries saw Muslims as followers of God, an ambiguity polemicists had to crush with totalizing ‘no half-truth’ theology.
• DEFINE: Shows that the hard Christian exclusivism familiar from later tropes was itself polemical labor, not settled consensus—the ‘there can be no truth outside Christianity’ stance required active argument against softer views.