POINCARÉ-WEYL’S PREDICATIVITY: GOING BEYOND

Abstract

. On the basis of Poincar´e and Weyl’s view of predicativity as invariance, we develop an extensive framework for predicative, type-free first-order set theory in which Γ 0 and much bigger ordinals can be defined as von-Neumann ordinals. This refutes the accepted view of Γ 0 as the “limit of predicativity”.