The Lagrangian, constraint qualifications and economics

Abstract

Considering constrained choice, practitioners and theorists frequently invoke a Lagrangian to generate optimality conditions. Regular use of that vehicle requires, however, some constraint qualification. Yet many economists go easy on the mathematics of that issue. Conversely, few mathematicians elaborate on the economics of the context. Thereby both parties leave some lacunas as to didactics or intuition. This note attempts to shed some light on these matters.