In his commentaries on Porphyry and Aristotle’s Organon and in his other works, John Duns Scotus shows his knowledge of both the modistic theory of language and the theory of supposition. My contribution sheds some light on the relationship between Scotus’ philosophy of language and the theory of supposition, collecting and commenting on all the passages in which he makes use of it or discusses some theoretical points. I take into special account the almost unknown commentary on the Topics, which (...) is preserved in a Vatican manuscript. (shrink)