A very detailed account of main developments of logic will be found in Logic, History of. Brief explanations of many of the terms commonly used by logicians will be found in Logical Terms, Glossary of. The Encyclopedia also features the following articles dealing with questions in logic and the foundations of mathematics: Artificial and Natural Languages; Combinatory Logic; Computability Theory; Computing Machines; Decision Theory; Definition; Existence; Fallacies; Geometry; Gödel's Theorem; Identity; Infinity in Mathematics and Logic; Laws of Thought; Logical Paradoxes; Logic Diagrams; Logic Machines; Many-Valued Logics; Mathematics, Foundations of; Modal Logic; Negation; Number; Questions; Semantics; Set Theory; Subject and Predicate; Synonymity; Syntactical and Semantical Categories; Types, Theory of; and Vagueness. See "Logic" and "Mathematics, Foundations of," in the index for entries on thinkers who have made contributions in this area.