The different treatments of glass—verre églomisé and transparent—within reli-quaries such as the Metropolitan Museum of Art’s diptych may initially seem to
be at aesthetic odds with one another. On the one hand, the portions of trans-parent glass allowed ambient light to penetrate the glass and illuminate the small relic fragments and authentics. On the other hand, the areas of the glass decorated with gilding would have produced glowing golden reflections evocative of God’s presence when struck by light. By combining these two different treatments the reliquaries simultaneously served as a window to the relics and as a mirror of the divine, making them well suited to contemporary visuality and, by extension, very powerful devotion aids.
As described in Chapter 5, a reliquary with relic windows made of transpar-ent glass could have compelled the viewer to look through the glass’s surface to the relic fragments of wood, cloth, and hair. Because of the small size of the relics, the trecento viewer needed to get close and perhaps even strain one’s eyesight in order to see the relics. Such intense gazing likely lent the process of viewing the panel a very intimate and intense tone. An emphasis on careful, engaged, and active looking would have been further emphasized because, in order to obtain validation of the relics, the viewer needed to be literate and read the text written on the authentics. Further stress on the visual experience derived from the fact that, unlike earlier forms of relic worship these relics did not offer the viewer an opportunity to touch, kiss, or ingest the holy fragments. Set behind the glass plate, these precious fragments were only available to one’s sense of sight.
In a general way this type of spiritual devotion—so dependent on one’s phys-ical sense of sight—may be seen as evocative of an empirphys-ical viewing experience and perhaps even a harbinger of the growing interest in scientific investigation usually equated with a Renaissance outlook.26 Encountering the relics in this con-text allowed the viewers to use their eyes to see, or to know, the human side of Christ and the saints by engaging with evidence of their material form as a means of contemplating the divine. Fourteenth-century viewers could have established a powerful connection with their spiritual role models, and ultimately Christ, through examining material evidence of their shared human experience.
In a manner very different from the transparent portions of glass, the areas of the reliquary’s glass decorated with verre églomisé depict canonical Chris-tian narratives and emphasize the surface of the glass panel. When viewing the golden reflections bouncing off the gilded imagery one would have witnessed the sharp, bright instances of light. Paul Hills suggests that such an experience could have been interpreted as a powerful connection between the viewer and the holy image because light and spiritual enlightenment were commonly associated with one another at this time.27 Such gilded imagery could have reminded the four-teenth-century viewer of more traditional medieval reliquaries which typically
concealed relics behind an array of precious materials such as gold in order to evoke the precious nature of the divine.28 Using their inner mind’s eye and spiri-tual insight the faithful viewer could reflect on the divine nature of God in a more abstract way.
Thus the transparent glass provided viewers with an opportunity to use their sensory perception to examine physical evidence of the saints’ human nature while the golden highlights had the potential to abstractly symbolize the divine.
By treating the glass in these two distinct ways the artist offered the viewer two dramatically different—but equally valid—visual experiences capable of inspiring spiritual insight: one through reflection on Christ’s humanity and the other on his divinity. One wonders if the trecento viewer struggled to reconcile them or, per-haps, privileged one over the other. If the principles behind early modern Chris-tian doctrine can serve as a model, it is likely that a fourteenth-century viewer did not expect cohesion and may have even appreciated a paradoxical approach when contemplating spiritual matters. After all, the reliquary’s primary function was to commemorate the relics, the physical evidence of the human nature of Christ and his saints. At the same time the reliquary needed to appropriately celebrate the corresponding celestial spirit. By fusing the two different decorative treatments within a single sheet of glass the reliquary could have elegantly evoked the central mystery of the Christian faith: the nature of Christ as both fully human and fully divine. And, in so doing, it referenced the medieval tradition’s penchant for a more abstract approach to the divine with the golden highlights as well as a more empirical approach indicative of burgeoning Renaissance values.
It is possible there were other correlations between the different treatments of the glass and the two main visual theories of the day—intromission and extramis-sion—as well as with the early modern anatomical understanding of the eye. As noted in Chapter 3, the Platonic model of visual theory known as extramission permeated Western European thought from the fourth century through the end of the thirteenth century. Plato theorized that the eye sent out visual beams that coalesced with external light and reached out to the object, resulting in visual perception.29 Thus when praying before a reliquary, trecento viewers sympathetic to Plato’s visual theory would have been able to conceive of the dramatic golden reflections as more than just indications of the holiness of the reliquary. These sharp rays of light bouncing off the glass could have been understood as visual manifestations of Plato’s fiery rays emitted from the eye, hitting their object of perception, and returning to the viewer with the input. In this context, the reli-quary’s gilding offered visual verification of the moment of contact between the viewer and the reliquary thereby ensuring a solid foundation for one’s devotional
practice. That Plato’s visual theory resonated with the golden highlights from the verre églomisé portions of glass rather than the transparent glass is fitting because Plato’s philosophical outlook was more concerned with abstract concepts rather than observable phenomenon.
If, however, instead of God’s divine nature one aimed to reflect on the human-ity of Christ and the saints, the viewer could have reflected on the emerging phi-losophy and visual theory of Aristotle.30 As described in Chapter 5, Aristotle’s visual theory mostly superseded that of Plato by the beginning of the fourteenth century after its reintroduction to the Latin West through Muslim and ancient Greek optical treatises.31 Aristotle combined certain aspects of Plato’s extramission with its main theoretical opponent, intromission, which maintained that the per-ceived object sent forth images of itself, known as eidola, into the eye. In order to reconcile these two seemingly opposed systems, Aristotle developed what David Lindberg has termed the “mediumistic” visual theory. 32
Aristotelian theory asserted that the perceived object sent forth eidola, or images of itself, into the intervening medium—usually air—and it was through this medium that the visual properties were absorbed and processed by the eye.
Lindberg describes Aristotle’s position as one not focused on directional rays from the object or eye but rather one that paid more attention “toward the medium between the observer and the visible object.”33 As Lindberg describes it, Aristotle
“perceives the absolute necessity of this medium … [which is] diaphanous or transparent, a nature or power found in all bodies, but especially air, water, and certain solid substances.”34 For Aristotle’s theory, then, which was ascendant at the time of the fabrication of the Metropolitan’s Reliquary Diptych and similar verre églomisé reliquaries, a great deal of emphasis and importance was placed on the space between the viewer’s eye and the observed object. For visual contact to occur this medium needed to be transparent.
The ability of the Metropolitan’s Reliquary Diptych to resonate simultane-ously with both the Aristotelian and Platonic modes of vision is not a conceptual or devotional weakness but rather constitutes a fitting reflection of a historical context in which both theoretical models were available and possible. Though there was a general shift from the Platonic to the Aristotelian model, the debate between these two models continued from the time of the medieval scholastics until Johannes Kepler. Thus, throughout the fourteenth century, Plato’s theory was regarded as valid enough to dispute and therefore a premise worthy of serious consideration.35
When contextualizing these visual theories within the sphere of devotional art and the verre églomisé reliquaries it is important to note that visual theories
were not purely scientific pursuits but, rather, a means to a spiritual end. Devo-tional effectiveness superseded optical debate and purely scientific goals. The pri-vate nature of prayer afforded the viewer an opportunity to employ whichever theoretical model or models served the ultimate goal of bringing one closer to God. Even if the viewer had exposure to optical theories—which would have at least been somewhat likely if the viewer was an educated member of the Francis-can order—the devotee using the reliquary would not have necessarily been con-cerned with the specifics of the theoretical models while deep in prayer. Rather, when faced with the potential for spiritual enlightenment the trecento devotee would have likely employed any and all methods at his or her disposal to affect spiritual enlightenment.36
As mentioned in Chapter 4 there was another aspect of optical science that could have resonated with the viewer’s experience of the transparent glass relic windows, namely, the anatomy of the eye. The ancient scholar who codified much of the early modern understanding of the eye’s anatomy was Galen, however, the Latin West obtained most of its information on the eye’s structure from Hunain’s Ten Treatises on the Eye.37 Hunain described the lens of the eye as an ice-like or crystal-like humor which is uncolored, transparent, luminous, and round with a flattened face.38 Its transparent nature, he noted, allowed it to quickly receive the color of perceived objects while its round shape prevented breaking or chipping and its flatness provided an ideal surface for receiving visual stimuli.39 As the seat of vision the crystalline humor occupied the central position in the eye so that it could be served by the other elements.40
After the crystal-like humor, the next most important supportive membrane was the one located directly behind the lens. This element was described as the vitreous humor, that is, an component having a glass-like nature. Although the glass-like substance within the eye was not considered the location where vision occurred it was nevertheless crucial for fostering the visual process. The vitreous membrane served the crystalline humor by mediating between the seat of vision and the blood vessels of the retina. As Hunain explained, “A substance is most quickly transmitted into the thing which resembles its own nature most closely.” 41 The eye’s glasslike substance was ideally suited to serve the crystalline seat of vision because the material of glass was similar to, but not identical to, the properties of crystal.
Knowledge of the eye’s glasslike component could have resonated with the glass panels of the reliquaries. As the faithful gazed at the relics through the glass they could imagine that the glass panel fostered a form of visual contact. One thinker supporting the notion that vision was a form of contact was Alexander of
Hales. In the thirteenth-century debate over the benefits of viewing the Elevation of the Host, Hales argued that visual contact was sufficient to receive the host’s virtues. He explained that because the Eucharist bestowed spiritual, immaterial benefits, the sense of sight was the most appropriate sense organ with which to receive them, as it was the most immaterial of the five senses.42 The belief that viewing the relics constituted contact with them would have been especially help-ful to one viewing the small fragments within the verre églomisé reliquaries.
While it is difficult to ascertain the extent of critical engagement among trecento viewers with the aforementioned optical theories, the Franciscans were some of the most interested in studying and capitalizing on an understanding of optics for their devotional pursuits. As noted elsewhere in this book, the Francis-can order, the likely patrons and viewers of many of the verre églomisé reliquaries, had a strong penchant for visual media and optics.43 Therefore questions about the relationship between their reliquaries and their notion of vision are important ones.