|Provability: Logic statements are only provable within the system to which they belong. The question then is, among other things, whether the means of expression of the system are sufficient for the presentation of evidence to the statements.|
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Provability / Field: it is more natural to explain it in terms of the possible existence of strings of symbols as by an actual existence of an abstract sequence of abstract analogues of such characters (symbols).
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