Dominique Demange

did roger bacon and peter john olivi ever meet? We suggest a positive answer to this question. After he became a Franciscan in 1257, Roger Bacon spent ten years at the Franciscan Paris convent. In those years he wrote the De multiplicatione specierum —his most thought-out piece—the Opus majus, Opus minus, and Opus tertium, which he completed by early 1268. It is not clear whether Bacon returned to England after 1268, or remained in Paris until 1280.1 Peter John Olivi wrote the Summa questions in several phases.2 According to Sylvain Piron's chronology, Olivi's questions on Physics should be dated before 1270, and his theory of...

In some passages of the Opus maius and the Opus tertium, Roger Bacon holds that mathematical objects are the immediate and adequate objects of human’s intellect: in our sensible life, the intellect develops mostly around quantity itself. We comprehend quantities and bodies by a perception of the intellect because their forms belong to the intellect, namely, an understanding of mathematical truths is almost innate within us. A natural reaction to these sentences is to deduce a strong Pythagorean or Platonic influence in Roger Bacon’s theory of mathematical knowledge. However, Bacon has always followed Aristotle’s view according to which numbers and figures have no real existence apart from the sensible substances, and universal knowledge comes from sensory experience as well. It appears that Bacon’s claim that quantity is the first object of human's intellect comes from an original reading of a passage of Aristotle’s On Memory and Reminiscence. In this paper, we try to clarify Bacon’s views about mathematical abstraction and intellectual perception of mathematical forms in his Parisian questions on Physics and Liber De causis, the Perspectiva, Opus maius, Opus tertium, the Communia mathematica and the Geometria speculativa. We conclude that Bacon considered mathematical abstraction as a mode of perception of the internal structure of the physical world: mathematical abstraction does not mean for Bacon an act of separation of ideal forms from the sensible matter, but a possibility of intuition of the internal structure of the sensible world itself, a faculty which is necessary for human’s perception of space and time.

A quelle certitude puis-je pretendre dans la connaissance des phenomenes naturels? De quelle nature sont les premiers principes de la connaissance, et comment les connait-on? Comment une proposition scientifique, en se rapportant a un objet de connaissance, atteste-t-elle ainsi de sa verite objective? Qu'est-ce qui fait l'unite d'une science en general, au-dela de la multiplicite des connaissances qui la constituent? Sur quel fondement se definissent et se separent les sciences speculatives reelles (metaphysique, physique, mathematique)? En vertu de quelle structure la logique et la metaphysique sont-elles articulees? Telles sont quelques unes des questions fondamentales qui innervent la theorie du savoir de Jean Duns Scot et manifestent l'importance et l'acuite de sa speculation epistemologique. A ne pas se focaliser sur la seule dimension metaphysique de la pensee du Docteur Subtil, et a la reinscrire bien plutot a l'interieur de sa theorie de la connaissance, de ses concepts et de ses problemes, on pourra s'apercevoir alors qu'au-dela de la refondation de la metaphysique par l'univocite de l'etant, un geste plus important encore s'est produit chez Duns Scot: une autonomisation des principes de la connaissance objective sur la metaphysique, autonomisation qui ouvre un espace metaphysiquement neutre: celui de la pure possibilite objective en general.

This article attempts to understand the extent to which, and the terms in which, it was possible to speak of sensory vision as a psychic representation before Johannes Kepler inaugurated the new optics in his famous Paralipomena ad Vitellionem (1604). The following argument is taken as a starting point: That it is only within this new paradigm, dissociating the physical process of vision from its psychic treatment, one can legitimately speak of vision as a mental construction or a representation. After examining this question in the light of several ancient and medieval theories, the article reaches a different conclusion. The question of vision as a mental representation dates as far back as Aristotle, conferring to the internal senses (phantasia, common sense) the major function in elaborating the content of perception. Additionally, some theories under neo-Platonic influence, such as those of Augustine or Avicenna, clearly conceive direct vision as a psychic representation. In Paralipomena ad Vitellionem, Kepler distinguishes optics as a physical science of light from the psychology of perception; but the latter has already a long history, as does the idea of vision as a mental representation.