Psychology Dictionary of Arguments

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Impredicativeness: Impredicatives are concepts which are defined only by means of the propositional sets to which they themselves belong. Problems arise in connection with possible circular conclusions. To avoid paradoxes, the demand is sometimes made to avoid impredicative concepts. See also Paradoxes, Russellian Paradoxy, Poincaré.
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Annotation: The above characterizations of concepts are neither definitions nor exhausting presentations of problems related to them. Instead, they are intended to give a short introduction to the contributions below. – Lexicon of Arguments.

 
Author Concept Summary/Quotes Sources

Hartry Field on Impredicativeness - Dictionary of Arguments

I 214
Def impredicative/Field: completely impredicative properties: are not at all derived from previously available properties. - In particular, there is no property to be a property.
Quasi-impredicative: also allows "property to be a property".
>Self-reference
, >Predication.
I 216
Classic example for impredicative definition: E.g. What is it for an ordinal number to be finite?

Fin (ON) P [P is inductive & P (0)> P (ON)]

whereby P is inductive is defined as:

b [P(b) > P(b + 1)]

((s) All successors have the same property (to be a number)).
The invalid objection against the impredicative definition (> VsImpredicativity) is that one cannot know that a given number, e.g. 2 is finite because, in order to show this, we must be able to show that 2 has every inductive property of 0.
To show that 2 is finite, we must show first that exactly this 2 is finite (circular).
Solution/Field: the solution is simple: if finiteness is an inductive property, then 2 is finite. - No circle.
>Induction, >Deduction, >Circular reasoning, >Predicativeness.

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Explanation of symbols: Roman numerals indicate the source, arabic numerals indicate the page number. The corresponding books are indicated on the right hand side. ((s)…): Comment by the sender of the contribution. Translations: Dictionary of Arguments
The note [Concept/Author], [Author1]Vs[Author2] or [Author]Vs[term] resp. "problem:"/"solution:", "old:"/"new:" and "thesis:" is an addition from the Dictionary of Arguments. If a German edition is specified, the page numbers refer to this edition.

Field I
H. Field
Realism, Mathematics and Modality Oxford New York 1989

Field II
H. Field
Truth and the Absence of Fact Oxford New York 2001

Field III
H. Field
Science without numbers Princeton New Jersey 1980

Field IV
Hartry Field
"Realism and Relativism", The Journal of Philosophy, 76 (1982), pp. 553-67
In
Theories of Truth, Paul Horwich, Aldershot 1994


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