# cogency

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**Empiricism**— John Locke, a leading philosopher of British empiricism This article is about the field of philosophy. For the album by Borknagar, see Empiricism (album). Empiricism is a theory of knowledge that asserts that knowledge comes only or primarily via …52

**First-order logic**— is a formal logical system used in mathematics, philosophy, linguistics, and computer science. It goes by many names, including: first order predicate calculus, the lower predicate calculus, quantification theory, and predicate logic (a less… …53

**Gödel's completeness theorem**— is a fundamental theorem in mathematical logic that establishes a correspondence between semantic truth and syntactic provability in first order logic. It was first proved by Kurt Gödel in 1929. A first order formula is called logically valid if… …54

**Ludwig Wittgenstein**— Wittgenstein redirects here. For other uses, see Wittgenstein (disambiguation). Ludwig Wittgenstein Photographed by Ben Richards Swansea, Wales, 1947 Born 26 April 1889 …55

**Logical connective**— This article is about connectives in classical logic. For connectors in natural languages, see discourse connective. For connectives and operators in other logics, see logical constant. For other logical symbols, see table of logic symbols. In… …56

**Propositional calculus**— In mathematical logic, a propositional calculus or logic (also called sentential calculus or sentential logic) is a formal system in which formulas of a formal language may be interpreted as representing propositions. A system of inference rules… …57

**List of philosophy topics (A-C)**— 110th century philosophy 11th century philosophy 12th century philosophy 13th century philosophy 14th century philosophy 15th century philosophy 16th century philosophy 17th century philosophy 18th century philosophy 19th century philosophy220th… …58

**Logical positivism**— (also known as logical empiricism, scientific philosophy, and neo positivism) is a philosophy that combines empiricism the idea that observational evidence is indispensable for knowledge with a version of rationalism incorporating mathematical… …59

**Intuitionism**— This article is about Intuitionism in mathematics and philosophical logic. For other uses, see Ethical intuitionism. In the philosophy of mathematics, intuitionism, or neointuitionism (opposed to preintuitionism), is an approach to mathematics as …60

**Mathematical logic**— (also known as symbolic logic) is a subfield of mathematics with close connections to foundations of mathematics, theoretical computer science and philosophical logic.[1] The field includes both the mathematical study of logic and the… …