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|Object Language||I 100
object language / / metalanguage / Field: E.g. proof theory: here there is no object level - object level: here the statements do not refer to propositions or formulas - and thus not to axioms, rules of inference or derivatives - Proof Theory: works with mathematical entities.
axiom / (s): not part of the object language (OL) - Schematic formula: can be part of the object language - Field: this detects the concept of truth better.
Realism, Mathematics and Modality Oxford New York 1989
Truth and the Absence of Fact Oxford New York 2001
Science without numbers Princeton New Jersey 1980