Despite renewed efforts to establish world literature, most of the presently available theoretical models do not provide solid concepts as to the meaning and relevance of this approach. After a critical review of recent publications, this article analyzes a unique and most revealing case, the reception of medieval Persian literature (Sa'dī) through translations into European languages beginning in the seventeenth century, primarily by the German diplomat, traveler, librarian, philologist, and linguist Adam Olearius. Here we can observe what truly constitutes world literature, with Sa'dī serving as a major literary inspiration for early modern reflections on virtues and vices, relevant also for Western audiences. He was not a Christian, but the poet's truly noble ideals were to have a deep impression on his future readers in East and West, especially since the early modern age. [ABSTRACT FROM AUTHOR]