The Polish Peasant in Europe and America is one of the foundational works of American and world sociology, famous for its innovative qualitative methodology. Its authors proposed new theoretical ideas, including a concept of social causality and a new theory of personality combining a biologistic concept of temperament with a culturalist concept of character. Interpreters of the book still disagree about the extent of each author’s actual contribution to the work and about its scientific status in light of modern sociological theories. This article claims that to understand the book one has to take into account the previous intellectual trajectories of both authors. As a theoretical dialogue between representatives of two contrary approaches, the work may serve as an alternative to the supposed theoretical “convergence” offered two decades later by Talcott Parsons.