Medieval writers deemed useful fabrication likely true precisely because it harmed enemies

Evidence

Yet they were unable to bring themselves entirely to relinquish more damning testimony from Christian sources: testimony that would have been more damning had it been, in the modern sense, reliable; but which Muslims, like modern scholars, could never have considered other than a ridiculous travesty of fact. The most probable explanation of what happened must be that Christians thought that whatever tended to harm the enemies of truth was likely itself to be true. — Norman Daniel, Islam and the West, 1372

Categorization

• DEEPTHINKING: A precise mechanism for epistemic corruption: a truth-criterion (‘harms the enemies of truth, therefore true’) that structurally guarantees distortion. This is the operating logic of the constitutive outside.
• XREF: Provides the mechanism-level genealogy for the vault’s claim that the figure of the Muslim enemy is produced, not discovered — the epistemological rule that generates it is stated here.
• SEED: Essay angle on how a community’s criterion of truth can be inverted so that instrumental usefulness for the ingroup becomes evidence of veracity — a general theory of polemical epistemology.