|Expression: phrase, word, formula, or part of a formula. Below the level of sentences, therefore not true or false.|
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linguistic expressions / Tarski: are physical objects - Proposition: ideal objects - truth only in respect of a particular language - truth semantically: fundamentally different from fulfillment, designation, definition - Mathematics: provability and truth often fall apart - metalanguage because the object language must not contain the truth predicate (Vsself-referentiality).
Logic, Semantics, Metamathematics: Papers from 1923-38 Indianapolis 1983