French churchman, philosopher, and critical thinker, called Doctor facundus (“eloquent teacher”), who was important as a forerunner to William of Ockham.

Petrus may have become a Franciscan at Gourdon before 1300; he was in Paris (1304) to study, possibly under John Duns Scotus. He became lector at Bologna (1312), Toulouse (1314–15), and Paris (1316–18). Provincial of his order for Aquitaine c. 1320, he was nominated archbishop of Aix-en-Provence and consecrated in 1321 by Pope John XXII, to whom he had dedicated c. 1316 his Commentariorum in primum librum sententiarum, 2 vol. (1596–1605; “Commentary on the First Book of Sentences”).

Criticizing Duns Scotus' and St. Thomas Aquinas' theory of knowledge, Petrus promoted an individualistic empiricism (emphasizing the part played by experience in knowledge against that played by reasoning), supported by a doctrine of universals, or general words that can be applied to more than one particular thing; this doctrine is partly Nominalistic (denying the reality of universal essences) and partly conceptualistic (acknowledging universals as existing only in the mind). According to Petrus, knowledge is appearance of objects: man knows what exists by direct impressions, more or less clearly, but without intermediaries; forms, essences, and universals are fictions. Although some of his philosophical theories are individual, he generally conforms to the dictum subsequently known as “Ockham's razor”—i.e., that plurality should not be posited without necessity. Essentially, Petrus anticipated the Nominalism that Ockham developed more fully.

Petrus' works include Tractatus de paupertate (1311; “Treatise on Poverty”), the unfinished Tractatus de principiis naturae, 4 vol. (“Treatise on the Principles of Nature”), and Tractatus de conceptione beatae Mariae Virginis (1314/15; “Treatise on the Conception of the Blessed Mary the Virgin”). In 1319 he wrote his popular Compendium . . . totius Scripturae (“Compendium . . . of the Whole Scripture”).