It is relatively well known that Buridan’s nominalist semantics changed “the rules of the game” in practically all fields of philosophy and science. For instance, in his semantics, the traditional distinction between essential and accidental predicates is mapped onto the Ockhamist distinction between absolute and connotative terms and concepts. It is, however, still not quite well understood what impact these “new rules” had in particular philosophical disciplines. This essay offers a case study of the late-medieval paradigm change brought about by nominalist “semantical innovations.” In particular, it contrasts Aquinas’ “semantics-driven mereology” with Buridan’s, set against the background of Buridan’s new, nominalist semantics, arguing that the two authors’ differences in their mereological considerations are rooted in the differences between their diverse semantic intuitions. The conclusion of the essay will provide a brief logical and historical evaluation of the paradigmatic changes brought about by these diverse intuitions.