Giles of Rome commented the four books of the Sententiae in Paris, in 1269-1271. The edition of the reportatio of his lectures, published in 2003, is herewith complemented by the edition of his principium, that is, the inaugural address he held in the fall of 1269, shortly before starting his course. Giles’ principium is a general introduction to the four books of the Sententiae ; based on the exegesis of Sap. 4, 3, it develops two themes : (1) knowledge of theology by negation of the human sciences, (2) knowledge of the four causes of theology by negation of the four causes of the human sciences. Following the edition of Giles’ principium is the edition of an anonymous’ principium, at first (but wrongly) attributed to Giles himself.