In the first half of the 15ᵗʰ century there was a coherent philosophical system of teaching at the Jagiellonian university, so-called ars vetus, concerning the interpretation of three treatises: Aristotle’s Categories and Hermeneutics and Porphyry’s Isagoge. The question-commentaries on the Categories that have been preserved in several manuscripts show astonishing similarity in solving individual problems – there are three copies of Benedict Hesse’s commentary and one copy of Paul of Pyskowice’s work, moreover, in BJ 1941 there is an anonymous commentary (...) on the Categories that is also very close to the ones mentioned before, to prove that fact. This paper, discussing the four-fold division of opposition in those Polish commentaries on Aristotle’s Categories, is part of the studies on the manuscript material that has not been critically edited yet. The main goal is to show the philosophical views on contraries, contradictories, relatives and possession and privation in a wider perspective, comparing the Polish commentaries’ doctrine with the authoritative text itself. (shrink)