|Classes: identity of classes provided by same elements (extension) - identity of properties by the same predicates (intension).|
|Quine, Willard Van Orman
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Class abstraction attributed to singular descriptions: (iy)(x)(x from y iff ..x..) - instead: x^(..x..) - does not work for intensional abstraction.
Difference classes/properties: classes are identical with the same elements - properties not yet identical if they are assigned to the same things.
Classes: one could reinterpret all classes in their complement: "no element of .." - you would never notice anything - Bottom layer: every relative clause, every general term determines a class.
Russell (Principia Mathematica) classes are things: they must not be confused with the concept of class - However: paradoxes also apply to class terms and propositional functions not only for classes -
Incomplete symbols (explanation by use) - to explain away classes.
Classes/Quine: simplify our access to physics - but are still a myth.
Classes/Quine: no accumulations or collections! E.g. the class of stones in a pile cannot be identified with the pile: otherwise another class could also be identified with the same pile: e.g. the class of stone molecules in the pile - the validity theory applies to classes, but not to the individual sentences - predicates are not names of classes, classes are the extension of predicates - classes are assumed to be pre-existent (see below).
Classes/relations/Quine: are real objects if values of bound variables.
Class/individuals/Quine: everything is class! if we understand individuals to be identical to their class of one (i.e. not elementless).
Classes/Quine: quantification through classes allows for terms that would otherwise be beyond our reach.
Wort und Gegenstand Stuttgart 1980
Theorien und Dinge Frankfurt 1985
Grundzüge der Logik Frankfurt 1978
Mengenlehre und ihre Logik Wiesbaden 1967
Die Wurzeln der Referenz Frankfurt 1989
Unterwegs zur Wahrheit Paderborn 1995
From a logical point of view Cambridge, Mass. 1953
Bezeichnung und Referenz
Zur Philosophie der idealen Sprache, J. Sinnreich (Hg), München 1982
Philosophie der Logik Bamberg 2005
Ontologische Relativität Frankfurt 2003