Relative Categoricity and Abstraction Principles

Many recent writers in the philosophy of mathematics have put great weight on the relative categoricity of the traditional axiomatizations of our foundational theories of arithmetic and set theory ([Par90], [Par08] §49, [McG97], [Lav99], [VW14]). Another great enterprise in contemporary philosophy of mathematics has been Wright’s and Hale’s project of founding mathematics on abstraction principles ([HW01], [Coo07]). In [Wal12], it was noted that one traditional abstraction principle, namely Hume’s Principle, had a certain relative categoricity property, which here we term natural relative categoricity. In this paper, we show that most other abstraction principles are not naturally relatively categorical, so that there is in fact a large amount of incompatibility between these two recent trends in contemporary philosophy of mathematics. To better understand the precise demands of relative categoricity in the context of abstraction principles, we compare and contrast these constraints to (i) stability-like acceptability criteria on abstraction principles (cf. [Coo12]), (ii) the Tarski-Sher logicality requirements on abstraction principles studied by Antonelli [Ant10b] and Fine [Fin02], and (iii) supervaluational ideas coming out of Hodes’ work [Hod84, Hod90, Hod91]. ∗Department of Logic and Philosophy of Science, 5100 Social Science Plaza, University of California, Irvine, Irvine, CA 92697-5100, U.S.A., [email protected] or [email protected] †Department of Philosophy, Northwestern University, 1860 Campus Drive, Evanston, Illinois 60208-2214, U.S.A., [email protected] 1 ar X iv :1 40 9. 34 83 v2 [ m at h. L O ] 2 4 Ja n 20 15