Jean-Michel Grandmont is well known for his contributions to monetary economics, disequilibrium macroeconomics, and microfoundations of macroeconomics. The purpose of the article is to focus on the latter aspect of Grandmont’s work and to provide a contextualized account of it as a specific answer to challenges in GET and in macroeconomics. After Werner Hildenbrand, Grandmont has presented the distributional viewpoint on agents’ characteristics as a sound methodological basis for GET and macroeconomics. The present paper discusses the methodological aspects of Grandmont’s proposal and its consequences on the use of the rationality assumption in economics.