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Intuitionism/Putnam: here existence is intra-theoretical. - E.g. Tarski: "electron refers" is equivalent with "There are electrons". - Intuitionistic: there is a description D such that "D is an electron" in B1 is provable - that could be true with appropriate theory, even if there were no electrons.
Intuitionism/PutnamVs: takes a strong aprioristic attitude towards mental entities, namely "meaning". - Also a platonist ability to capture constructive relations between them.
Pro Intuitionism: Löwenheim-paradox does not appear because "existence of a model" means to have a proof method - object/meaning/description: objects in constructive mathematics are given by descriptions. - These must not be attached with mysterious "glue" - reference is here given by the sense and sense through a verification process, not by truth conditions - there is then no "gap" between theory and objects - ((s) Truth conditions: when they are formulated linguistically, the significance could be shifted according to the law by Löwenheim - procedure: non-linguistical).
Von einem Realistischen Standpunkt Frankfurt 1993
Repräsentation und Realität Frankfurt 1999
Für eine Erneuerung der Philosophie Stuttgart 1997
Pragmatismus Eine offene Frage Frankfurt 1995
Vernunft, Wahrheit und Geschichte Frankfurt 1990