SUMMARY — Among the heresies attributed to Jan Hus, which were solemnly read in the Cathedral of Constance on the 6th July 1415, before being condemned to the stake, there was a most serious trinitarian-christologic error ascribed to him by a nameless «doctor in theolo-gia» («probatur per unum doctorem in theologia», said the official reader). On hearing being attributed to him such error, about which no question had been raised during the trial, Hus demanded with an angry voice: «Nominetur ille doctor*, but his request was not granted, and consequently the «doctor ille» remained in perfect anonymity (I). In the present study, the author proposes the identification of the «doctor ille» with a Spanish franciscan friar and master in theology, Diego Moxena, on the grounds of three types of proofs: firstly, on the 28th November 1414, immediately after the imprisonment of Hus, Diego, being entrusted by the cardinals of the council with the task of probing the opinion of the accused, presented himself in the prison as a simple friar without declaring his proper identity and, among other things, inquired of Hus what he thought about the Trinity and the Incarnation (II); secondly, on the 27th March 1415, the King of Aragon Ferdinand I, instigated by Diego, his «orator» at Constance, wrote a very strong letter to King Sigismund, lord of the council, asking him insistently to grant permission, notwithstanding the safe-conduct already given by him, that Hus be immediately condemned because he was defending horrible heresies: however, the only one of which explicit mention is made is precisely the trinitarian-christologic heresy (III); thirdly, the same error is attributed to Hus and attacked in four «cantilenae» or anonymous Latin rythms, which can be demonstrated as having been composed by the same Diego at Constance (IV). In an Appendix are published the four «cantilenae».
