Writing: (symbol with t">
|Equivalence: Relation between sentences. It exists if both sides have the same truth value, so that they are both true or both false._____________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. |
Peter Geach on Equivalence - Dictionary of Arguments
Equivalence/Biconditional/GeachVsBlack: "is material equivalent" is not synonymous with "if and only if".
Writing: (symbol with three lines) ≡ is often read as "materially equivalent".
Equivalence exists only between sentences, not the names of sentences.
Problem: "Tom loves Mary ↔ Mary loves Tom" is only significant if "≡" (three lines) is read as "iff" (if and only if) rather than "materially equivalent"(⇔)._____________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.
Logic Matters Oxford 1972