Classical logic

Classical logic identifies a class of formal logics that have been most intensively studied and most widely used. They are characterised by a number of properties; non-classical logics are those that lack one or more of these properties, which are:

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• Law of the excluded middle;
• Law of noncontradiction;
• Monotonicity of entailment and Idempotency of entailment;
• Commutativity of conjunction;
• De Morgan duality: every logical operator is dual to another.
 
Classical logic: Examples of classical logics ►