The desire to make visual contact with relics was just one facet of a larger cultural phenomenon. Over the course of the thirteenth and fourteenth centuries, Chris-tians sought out various ways to employ their sense of sight in pursuit of spiritual understanding and enlightenment. The result was a culture that was interested in optical theory and putting the study of this theory into practice. Many scholars have commented on the increasingly visual nature of late medieval society; one of the earliest was Johan Huizinga, who understood the trecento’s interest in visual infor-mation as a decline in culture of sorts.36 Writing about fifty years after Huizinga, Alfred Crosby takes a different approach and correlates the growing prominence of the visual sense with the need to quantify goods and other entities in his book, The Measure of Reality: Quantification and Western Society, 1250–1600.37 Crosby outlines a shift from a culture dominated by sounds—where holy scripture is delivered by sermon, decrees are announced at public gatherings, and time is kept
according to the ringing of the town bell—to one where the sense of sight pro-vides the most important types of information—where educated Christians read devotional treatises or prayer books, official documents are written and signed, and time is told by a clock or hourglass.
Hayden Maginnis’s art historical analysis, identifies and traces an emphasis on visual experiences throughout the fourteenth century’s seminal works of art, a period which he calls “an age of vision.” Maginnis demonstrates how a penchant for visual media manifested itself in various guises, from literature to painting.38 For instance, it was a visual encounter with a painting that was the primary cat-alyst for such important events as Saint Francis’s divine call to action and Boc-caccio’s poem, the Amorosa visione. Poems by Dante and Guido Cavalcanti also make numerous references to detailed visual descriptions, almost imploring their readers to envision their fictive worlds within the mind’s eye.39 When considering the popularity of visible relics and glass relic windows, it is important to cast a wide net and examine the ways these objects resonated with their larger, visually inclined cultural context. Doing so reveals that an interest in engaging with the world by means of vision was not unique to relic worship, but rather many aspects of trecento culture and religion were geared towards one’s sense of sight.
Mirroring trends in relic veneration, the sacrament of the Eucharist also began to cater to a more visually inclined audience. During the 1230s there was intense enthusiasm for the Elevation of the Eucharist, the moment during the mass when the priest raised the transubstantiated host to the crowd, showing them the mirac-ulous moment of transition from piece of bread to the body of Christ. The act of viewing the Elevation had become such a priority for the congregation that many faithful Christians ran to several different churches in a single day in order to see as many rituals as possible.40 It reached the point that some church leaders wor-ried the public was no longer interested in consuming the sacrament but content to solely view it.41 During the fourteenth century, the frantic need to rush from Elevation to Elevation subsided but the desire to see the Eucharist did not, as demonstrated by the proliferation of trecento monstrances that displayed the host behind rock crystal in an analogous manner as the relic windows.42
Both churchmen and scientists associated with religious orders found vision beneficial to cultivating divine understanding. Alexander of Hales (ca. 1170–
1245), a Franciscan theologian writing at the same time as the Elevation frenzy, advocated interacting with the Eucharist visually. Following ideas found in Aris-totle’s recently translated works, Alexander believed that a search for knowledge originated with one’s senses.43 He reasoned that Eucharist’s benefits were of a spiritual and immaterial nature and, therefore, the sense of sight was the most
appropriate sense for encountering the host, as it was the least material of the five senses.44 Roger Bacon (ca. 1120–1292), one of Alexander’s contemporary fellow Franciscans, also held the sense of sight and the ideas of Aristotle in high esteem.
Bacon described optics as “the flower of the whole of philosophy” because it sheds light on all the other scientific pursuits. For Bacon, one can “understand nothing fully unless its form is presented before our eyes,”45 and this applied to the pursuit of both heavenly and earthly knowledge.46
It is not a coincidence that both Alexander of Hales and Roger Bacon drew from Aristotle, or The Philosopher, as he was called at this time. Aristotle’s ideas began to permeate European thought around the middle of the thirteenth cen-tury when the majority of Ancient Greek and Arabic literature was translated to Latin.47 The arrival of Aristotelian ideas about the nature of reality and the sense of sight altered the trajectory of visual theory from what had been an essen-tially Neoplatonic system of extramission vision—where vision results from rays extending outward from the eye—to Aristotle’s version of intromission—where the eye receives information from the perceived object.
The theory of extramission vision, along with other Platonic ideas about real-ity, had dominated the Latin West due to the influence of Augustine (354–430) from the fourth century through the end of the thirteenth century when Aristo-telian ideas began to supplant them.48 William of Conches (ca. 1100–54) and Adelard of Bath (fl. 1110–40) were some of the first to deviate from pure extra-mission vision when they described in detail how visual rays not only leave the eye, but, upon making contact with the object, they returned to the beholder.49 Robert Grosseteste (ca. 1175–1253) continued this trend in the following cen-tury. His theories are still basically Platonic but he deviates by declaring his debt to Arabic sources.50 Albertus Magnus (ca. 1200–80) and, to a greater extent, Roger Bacon (ca. 1220–92), mark a significant turning point in western optics, one based more solidly on the intromission theories found in Aristotle and Arabic scientists such as Alhazen.51
Central to Aristotle’s theory, and important for the present discussion about glass, is the way in which the information is transferred from the object to the eye in the intromission model. Aristotle argued that vision occurs when the per-ceived object emits images of itself, known as eidola, into surrounding trans-parent media. As these entities make their way towards the eye, they alter the transparent medium until they reach the eye’s surface.52 Such a visual theory is less concerned with the direction of the visual rays and more focused on the integral role played by the transparent medium between the eye and object.53 As Aristotle described,
The evidence for this is clear; for if one puts that which has colour right up to the eye, it will not be visible. Colour moves the transparent medium, e.g., the air, and this, being continuous, acts upon the sense organ. Democritus is mistaken in thinking that if the intervening space were empty, even an ant in the sky would be clearly visible;
for this is impossible. For vision occurs when the sensitive faculty is acted upon; as it cannot be acted upon by the actual colour which is seen, there only remains the medium to act on it, so that some medium must exist; in fact, if the intervening space were void, not merely would accurate vision be impossible, but nothing would be seen at all.54
Thus, for Aristotle’s and his adherents, a great deal of importance was now placed on the medium between the eye and the observed object. And, importantly, for visual contact to be successful, this medium needed to be transparent.
Though it seems a logical candidate, I am not aware that either Aristotle or Bacon specifically mentioned colorless glass in reference to this transparent medium. Dante, however, does seem to have made such a connection. In Convivio III, ix, he describes a visual process very similar to that of Aristotle using glass as an example of the transparent medium, noting, “These visible things … enter the eye—I do not mean the things themselves, but their forms—through the diapha-nous medium, not actually but mentally, as through transparent glass.”55 The fact that Dante was familiar with current trends in visual theory and described them in vernacular prose suggests that this type of optical theory should not be seen as entirely inaccessible to the general educated public.56
Viewing reliquaries such as that by Naddo Ceccarelli (Figure 5.1) with an Aristotelian model of vision in mind, as Dante and like-minded viewers might have done, a fourteenth-century observer could have interpreted the relic win-dow as a stable, physical manifestation of the visual process, an affirmation that the relic was successfully sending forth its eidola into the surrounding medium, through the glass, and ultimately to the viewer’s eye. The fact that the eye’s anat-omy was thought to be made of crystalline and vitreous elements, as discussed in the last chapter, could have inspired even more confidence that the visual impression of the relic was received and processed by the viewer’s eye and mind.
Though it was not the seat of vision, the glass-like humor was a key component in facilitating the visual process because it was the intermediary between the observed object and the viewer’s body. In a similar way, the prominent round, glass relic windows in the reliquary facilitated one’s connection with the relics, which in turn are representations of the physical bodies of these saintly inter-cessors. Thus, the function of glass as a mediator, or a transmitter, pervaded an encounter with the reliquaries.