Martinus Jan Langeveld (1905-1989) was a key figure in Dutch academic educational studies after the Second World War. This article investigates the origins and sources of Langeveld's theory by examining his prior publications and the main references in conjunction with the intellectual movements of his time. This research shows, first, that Langeveld built his educational theory upon a variety of sources: the German-American psychologist William Stern (1871-1938), the Dutch educationalist Philipp Abraham Kohnstamm (1875-1951), the German philosopher Theodor Litt (1880-1962), and Edmund Husserl's (1859-1938) philosophy of phenomenology. Further, Langeveld borrowed a phrase from the medieval theology of Thomas Aquinas (1225-1274) as the key idea of his theory. Last, Langeveld's theory incorporates the important topics of the first decades of the twentieth century. In particular, the coinciding philosophies of personalism and phenomenology in the context of anti-positivist movements shed new light on Langeveld's theory.