Peter Abelard (Pierre Abelard, Abailard, Petrus Abaelardus), 1079-1142. Noted early medieval philosopher and theologian. He is popularly known for the ill-fated romance between him and his lover Heloise, which led to his castration. His scholarly work, repeatedly branded as heresy in his own time, consisted primarily of exegetical studies of Aristotle, Porphyry and others.