Abstract: This collection of newly commissioned essays, edited by NYU philosophers Paul Boghossian and Christopher Peacocke, resumes the current surge of interest in the proper explication of the notion of a priori. The authors discuss the relations of the a priori to the notions of definition, meaning, justification, and ontology, explore how the concept figured historically in the philosophies of Leibniz, Kant, Frege, and Wittgenstein, and address its role in the contemporary philosophies of logic, mathematics, mind, and science. The editors’ Introduction familiarizes the reader with the issues that are to be explored in detail in later parts of the anthology.

Keywords: a priori, Paul Boghossian, definition, Frege, justification, Kant, Leibniz, logic, mathematics, meaning, mind, ontology, Christopher Peacocke, science, Wittgenstein