ABSTRACT
This chapter explores how a specific development in the philosophy of pure mathematics at the turn of the twentieth century impinges on various analyses of economic rationality. It proposes to respond to Lawson's question by recourse to the philosophy of mathematics. The chapter distinguishes between the general issue of the rationality of recourse to convention per se in economic decision making from the specific issue of the specific rationale offered for recourse to a specific convention in a specific economic context. It introduces the reader to the divergent philosophical contexts of Humean and Lewisian analyses of convention. The chapter argues that the Keynesian and post-Keynesian recourse to convention is not only concerned with the establishment and maintenance of social stability. It focuses on Poincare's case for the existence or indispensable role of conventions in pure geometry. The chapter also argues that the same kind of ontological-epistemic indeterminacy is an integral component of the post-Keynesian non-ergodic world.
