|Equivalence: Relation between sentences. It exists if both sides have the same truth value, so that they are both true or both false.|
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|Horwich I 161
Material equivalent/T-schema/Thomson: "material equivalent" is itself defined in terms of truth.
Equivalence/equivalent/Thomson: E.g. twice the same expression, whereby once its definition was used instead of a part of it - that is not the form of instances of Tarski's truth definition.
P. Horwich (Ed.)
Theories of Truth Aldershot 1994