Crítica, Revista Hispanoamericana de Filosofía, Volume 35, number 103, abril 2003
What Finitism Could Not Be
[Lo que el finitismo no podría ser]
Matthias Schirn
Seminar für Philosophie, Logik und Wissenschaftstheorie
Universität München

matthias.schirn@lrz.uni-muenchen.de
Karl-Georg Niebergall
Seminar für Philosophie, Logik und Wissenschaftstheorie
Universität München

kgn@lrz.uni-muenchen.de

Abstract: In his paper "Finitism" (1981), W.W. Tait maintains that the chief difficulty for everyone who wishes to understand Hilbert's conception of finitist mathematics is this: to specify the sense of the provability of general statements about the natural numbers without presupposing infinite totalities. Tait further argues that all finitist reasoning is essentially primitive recursive. In this paper, we attempt to show that his thesis "The finitist functions are precisely the primitive recursive functions" is disputable and that another, likewise defended by him, is untenable. The second thesis is that the finitist theorems are precisely the universal closures of the equations that can be proved in PRA.
Keywords: finitist functions, primitive recursive functions, infinite totalities, finitist proof of the universal closure of an equation

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