When John Duns Scotus died at the young age of 42, seven centuries ago in 1308, he did not leave behind a completed body of work which would present his mature philosophical thought. Thus, the followers of Scotus were faced with the challenging task of interpreting the texts of the Subtle Docotr. Since Scotism became one of the most important schools of thought by the early modern period, the synthesis elaborated by the most famous of the commentators on Scotus’s philosophy Hugo Cavellus (1571-1626), Irish Franciscan and Archbishop of Armagh is of capital importance. Cavellus dedicated a considerable part of his commentary on the De Anima of Duns Scotus to the problems relating to the theory of the knowledge. Because of Cavellus’s central importance in seventeenth-century Scotism, his writings on doubt, evidence and certitude are noteworthy in terms of developments in modern thought .