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| | Logic - Open Encyclopedia (Site not responding. Last check: 2007-11-07) |
 | | Formal logic (sometimes called "symbolic logic") attempts to capture the nature of logical truth and inference in formal systems, which consist of a formal language, a set of rules of derivation (often called "rules of inference"), and sometimes a set of axioms. |
 | | For instance, propositional logic and predicate logic are a kind of formal logic, as well as temporal logic, modal logic, Hoare logic, the calculus of constructions, etc. Higher order logics are logical systems based on a hierarchy of types. |
 | | Informal logic is also more difficult because the semantics of natural language assertions is much more complicated than the semantics of formal logical systems, due to the presence of such phenomena as defeasibility. |
| open-encyclopedia.com /Logic (2307 words) |
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