 Abelard [Abailard], Peter |  Aristotle, General Topics: logic |  Boethius, Anicius Manlius Severinus |  conditionals |  conditionals: counterfactual |  grammar: typelogical |  Kilwardby, Robert |  logic: classical |  logic: conditionals |  logic: intuitionistic |  logic: many-valued |  logic: modal |  logic: paraconsistent |  logic: relevance |  negation 