Per beryllum intueamur. : The Metaphor of ‘Beryl’ in Nicholas of Cusa and the Cologne School in the Thirteenth and Fourteenth Centuries

In De beryllo (1458), Nicholas of Cusa uses a specific metaphor for knowing the world, that is, vision by looking through a "beryl"—a lens that is both concave and convex. The intellect of the one looking through it can reach a vision through the coincidence of opposites. This doctrine completes the reflection developed by Nicholas of Cusa in some of his previous works, such as De visione Dei (1453). In that same year, Nicholas of Cusa had also purchased a copy of Albert the Great's commentary on Ps.-Dionysius the Areopagite's De divinis nominibus, a text he refers to several times in De beryllo with the aim of defining human cognitio. In this paper, Nicholas of Cusa’s use of the "beryl" metaphor is defined and subsequently compared with the analogous use of the same metaphor by Albert the Great, Meister Eckhart, Theodoric of Freiberg, and in the sermons of the Carmelite Hane, collected in the Paradisus animae intelligentis. Finally, some remarks concerning the relevance of this metaphor in Cusa's philosophy are formulated.