Goodman's extensional isomorphism and syntactical interpretations

Abstract

The aim of the present paper is to provide a model-theoretic explication of Nelson Goodman's concept of extensional isomorphism. The term "extensional isomorphism" has been infomally introduced by Nelson Goodman in the beginning paragraph of his The Structure of Appearance. After some conceptual clarifications Goodman's concept of isomorphy turns out to be closely related to some variant of set-theoretic definability and some variants of syntactical interpretability.