propositional logic: Wikis

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Wiktionary

Up to date as of January 15, 2010

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Noun

 Singular propositional logic Plural propositional logics

propositional logic (plural propositional logics)

1. (logic) A formal deductive system in which formulae representing propositions can be formed by combining atomic propositions using logical connectives.

Simple English

Propositional logic is a formal system in mathematics and logic. Other names for the system are propositional caclulus and sentential calculus. The system is made of a set of propositions. Each proposition has a truth value, it is either true or false. Propositions can be joined together using logical connectives to make new propositions. Examples for logical connectives that are used often are logical and, logical or, logical if, logical if and only if and logical not.

Propositional logic only looks at the propositions and how they are connected, it does not decompose the propositions. That way, the proposition All cats are dogs and the earth is a disc is made of two propositions, All cats are dogs, The Earth is a disc. These are joined together with AND.

There are other logic systems that build on propositional logic. One of these is Predicate logic, which defines logical predicates, and looks at how they can be applied to arguments. Another system is called modal logic. It introduces two new junctors it is possible, that and it is necessary, that.