How well was the field of optics understood during the European Middle Ages and Renaissance? And how was that understanding achieved? Until fairly recently, the answer to both questions was sought in the Perspectivist optical tradition that emerged during the late thirteenth century. At the textual core of this tradition was Alhacen’s De aspectibus, which formed the basis for the key derivative works of Roger Bacon, Witelo, and John Pecham. Varying in technical complexity, these works (perhaps with the exception of Bacon’s) were incorporated into university teaching from at least the fourteenth century. But the Medieval and Renaissance university was neither the only nor, perhaps, the most significant channel through that optical lore filtered down to European thinkers. Sermons could be a source for such lore, albeit presented piecemeal, and so could such literary works as the Roman de la Rose or Dante’s Divine Comedy. Not simply channels for the dissemination of technical knowledge, though, these sources were crucial to the spread of optical literacy and with it a widening respect for, and interest in, the science of optics. Accordingly, Chaucer’s audience could at least grasp his allusion to “Alocen [Alhacen] and Vitulon [Witelo] […] that writen [of] queynte mirours and of perspectives” in the Canterbury Tales without necessarily knowing precisely what either author had to say about such mirrors. It is in view of these points that this project discussed the various routes, from university classroom to church pulpit, by which optical lore and literacy were promoted during the Middle Ages and Renaissance.