>Equivalence.
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Philosophy Dictionary of Arguments

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Biconditional: notation ↔; a statement that is true if the two sides have the same truth value ("true" or "false"). The biconditional (also bisubjunction) is part of the object language. Contrary to that is equivalence (⇔) which belongs to meta language. A biconditional that is always true is an equivalence.
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Annotation: The above characterizations of concepts are neither definitions nor exhausting presentations of problems related to them. Instead, they are intended to give a short introduction to the contributions below. – Lexicon of Arguments.

 
Author Concept Summary/Quotes Sources

Peter Geach on Biconditional - Dictionary of Arguments

I 189f
Equivalence/Biconditional/GeachVsBlack: "is materially equivalent" is not synonymous with "if and only if".
>Equivalence.
"Three line" symbol ≡ is often read as "materially equivalent". But equivalence exists only between sentences, not names of sentences.
Problem: Tom loves Mary ↔ Mary loves Tom" is only significant if "≡" (thee line) is read as "iff" (if and only if) rather than "materially equivalent".(⇔)
cf. >Material
, >Formal, >Description level, >Content, cf. >Formalism, >Formal language, >Formal speech, >Conditional.

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Explanation of symbols: Roman numerals indicate the source, arabic numerals indicate the page number. The corresponding books are indicated on the right hand side. ((s)…): Comment by the sender of the contribution. Translations: Dictionary of Arguments
The note [Concept/Author], [Author1]Vs[Author2] or [Author]Vs[term] resp. "problem:"/"solution:", "old:"/"new:" and "thesis:" is an addition from the Dictionary of Arguments. If a German edition is specified, the page numbers refer to this edition.

Gea I
P.T. Geach
Logic Matters Oxford 1972


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Ed. Martin Schulz, access date 2024-02-27
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