This biography traces the intellectual trajectory of Ignace Meyerson from his early education in medicine and physiology to the development of his distinctive idea of historical psychology. Far from remaining confined to clinical and experimental research, Meyerson repurposed his scientific training into a tool for constructing a human psychology grounded in the historical comparative study of what he termed “works.” His grand project, which he only put into formal words late in his career, was crafted against the backdrop of twentieth-century French psychology with its growing specialization and fragmentation, yet his proposal was impressively broad and ambitious. Instead of reducing mental life to isolated mechanistic processes, Meyerson sought to investigate psychological functions in their plurality, variability, and transformation across all the domains of human activity—language, law, art, science, and religion. This entry reconstructs both the milestones of his personal and academic journey, profoundly shaped by exile, World War II and the institutional obstacles he faced in postwar French psychology, and the theoretical and methodological contributions through which he voiced a powerful alternative vision of psychology as a genuinely human science.