This article presents the interpretation of Herman Jean de Vleeschauwer (1899-1986) of Medieval philosophy during his career as a lecturer and professor of philosophy at the University of South Africa (UNISA) from 1951 to 1964. The study is done regarding De Vleeschauwer's publications and unpublished manuscripts relating to Medieval philosophy, as filed in Archive MSS Acc 32 at the UNISA Institutional Repository. Essentially, De Vleeschauwer was one of only two South African university lecturers in the 20th century who consistently included (...) the Middle Ages in the philosophy curriculum (the other was Martin Versfeld at the University of Cape Town, from 1937 to 1972). When précising his work in Medieval philosophy at UNISA for the designated period, it becomes clear that De Vleeschauwer's nuanced defence of Thomism was the matrix of his interpretation. This cornerstone, and his numerous other published and unpublished texts relating to the Middle Ages, show that De Vleeschauwer was an erudite commentator, competent lecturer and skilled specialist researcher in Medieval philosophy, as he was in early modern and modern philosophy (especially on Kant and Geulincx). As a scholar of Medieval philosophy, in particular, De Vleeschauwer had no equal in the 20th century South African context. CONTRIBUTION: This article contributes to the ongoing assessment of the characteristic and curious inattention to Medieval philosophy at South African (especially the historical Afrikaans) universities during the course of the 20th century. (shrink)