Medieval polemicists mapped Muhammad onto earlier named heresies.

Evidence

At times, the Cluniac position took the term heresy for granted: the denial of Christ’s divinity was ‘the sum of this diabolical heresy’, as the annotator in Ketton put it. The swmmula claimed to sum up ‘the heresy and diabolical fraud of the sect of the Saracens or Ismaelites’, and Peter the Venerable echoed his secretary’s phrases when he spoke of ‘this error of errors, these dregs of all the heresies’. This imagery was not just poetic fancy, but had an exactly definable sense: ‘regurgitating almost all the dregs of ancient heresies which, infected by the Devil, he had swallowed, with Sabellius he denied the Trinity, with his own Nestorius he rejected the divinity of Christ, with the Manicheans he disavowed the death of the Lord, although he did not deny His return to Heaven’. — Norman Daniel, Islam and the West, 1020

Categorization

• DEFINE: Shows how ‘heresy’ functioned not as rhetoric but as doctrinal classification — precise mapping to Sabellius, Nestorius, Manicheans.
• XREF: connects to: Medieval writers mapped Muhammad’s doctrines onto a catalogue of prior Christian heresies