Peter Abelard

Abelard's Sic et Non method — collecting apparently contradictory authorities and resolving them through dialectical analysis — is the direct ancestor of the scholastic quaestio that would structure all later medieval university theology.

"By doubting we come to inquiry, and by inquiry we arrive at the truth." (Sic et Non, Prologue)

Abelard's conceptualism — universals are sermones (significant utterances) that pick out real resemblances but are not themselves things — is the medieval halfway house between realism and nominalism, and it anticipates Ockham's later position.

"Universals are words (sermones), not things (res), though they signify things that truly exist in a common way." (Logica Ingredientibus, on Porphyry)

Abelard insisted that dialectical reasoning must be applied even to sacred texts. Faith without understanding is mere credulity. He pushed the claims of reason further than any twelfth-century contemporary, which is why Bernard of Clairvaux accused him of subjecting the Trinity to logical analysis.

"The first key to wisdom is assiduous and frequent questioning. … For by doubting we come to investigate, and by investigating we recognise the truth." (Sic et Non, Prologue)

Abelard's ethics of intention — sin lies in the consent of the will to what one knows to be wrong, not in the external act — is a proto-modern intentionalist ethics that foreshadows both Kantian deontology and later virtue-theoretic concern with the agent's inner states.

"We call the intention good, that is, right in itself, but the action we call good not because it contains within it some good, but because it issues from a good intention." (Scito Te Ipsum, ch. 3)