Peter Lombard's 'Sententiae' of the 12th century contained rigorous rules on the ordination of priests, which were followed by popes. The regulations also concerned the Piast Duke of Wroclaw and Archbishop of Salzburg, Wlodzislaw, as well as his peer from the time of their studies at the faculty of liberal arts at Paris, master Witelo. The current paper deals with the relations between Duke Wlodzislaw and Witelo. It also presents the whole of the duke's life and, in the case of Witelo, gives a detailed account of the period of his studies. Details of Witelo's later life are presented in a book by the author of the article, entitled 'Witelo filosofo dalla natura del XIII sec. Una Biografia', Wroclaw 1984.