This chapter explores the final phase of Oskar Lange’s intellectual journey in the Western world, focusing on his 1945 article “The Scope and Method of Economics” as a synthesis of his scientific project. Lange aimed to reconcile rigorous economic theory with social relevance by critiquing neoclassical assumptions and advocating for a socialist alternative. His methodological reflections emphasise that economics is both a social and theoretical science, highlighting the conditional nature of economic laws and warning against the dangers of relying on axioms detached from empirical reality. Lange’s critique of capitalist institutions, particularly the assumption of rationality, reveals his broader ambition: to develop a generalised economic theory that can transcend ideological divisions and justify socialist transformation. Although he did not complete his intended comprehensive treatise, his contributions—covering debates on capital, Keynesian economics, and welfare theory—illustrate a coherent intellectual trajectory. The chapter concludes by placing Lange’s return to Poland in 1945 within this framework, interpreting it as a deliberate effort to align theory with revolutionary practice. This reflects his lifelong tension between scientific rigour and socialist conviction. Ultimately, his legacy represents a nuanced critique of economic orthodoxy and a bold, yet often overlooked, vision for the field of economics.