Konstanty Michalski was one of the most influential medievalists in the field of philosophy during the first half of the twentieth century. In particular, he was with Pierre Duhem one of the great pioneers of the serious scholarly study of philosophy in the fourteenth century and he decisively contributed, through an incredibly patient labor, to the difficult disentanglement of the considerable stock of manuscripts that survive from this period. An indefatigable philologist with outstanding scholarship, he was the first to conduct an in-depth examination of an astounding quantity of manuscripts, which he located, identified, classified, attributed, dated, and sometimes summarized. A remarkable historical accomplishment indeed!