 artificial intelligence: logic and |  category theory |  choice, axiom of |  descriptions |  epsilon calculus |  Frege, Gottlob |  Gödel, Kurt: incompleteness theorems |  grammar: typelogical |  lambda calculus, the |  logic, history of: first-order logic |  logic: classical |  logic: deontic |  logic: dynamic epistemic |  logic: modal |  logic: second-order and higher-order |  metaphysics |  ontological arguments |  paradox: Skolem’s |  paradoxes: and contemporary logic |  possibilism-actualism debate |  possible worlds |  Principia Mathematica |  proof theory |  quantifiers and quantification |  Quine, Willard Van Orman |  rational choice, normative: expected utility |  reasoning: automated |  Russell, Bertrand |  semantics: Montague |  Tarski, Alfred |  type theory 