In truth, Goethe was overwhelmed by what he saw, and his initial reaction (recorded by Johann Baptist Bertram, friend of the Boisserée brothers and Schlegel intimate) shows his ability to be honest with himself:
"For the sake of one's own continued existence, one laboriously closes oneself off in one's latter days from the youth that has arrived to overthrow old age; one has tried, in order to maintain one's equanimity, to preserve oneself from all impressions of a new and disturbing nature; when, at a stroke, a completely new and previously unknown world of colors and figures appeared before me, which forced me from the accustomed path of my ideas and feelings ... and if this or that hand would reach out from the picture in order to smack me in the face, I would have deserved it."
Nevertheless, the "old pagan king," as Boisserée called him in a letter of 23 October 1814, was not converted. By the time his reactions to the collection appeared in print, in Über Kunst und Altertum in den Rhein- und Maingegenden, Goethe had found a way of putting things back in their proper perspective. Thus, the newly discovered marvels of "Old German" art would not compromise the priority of ancient art based on classical -- Greek and Roman -- models. In the "Heidelberg" chapter Goethe puts the "Old German" works in an art historical schema, and attributes to them a privileged position for having preserved the continuity of classical art through the depredations of the Dark Ages and the decline of naturalism in the Middle Ages.
So, what are the strengths? Goethe saw something that was not at all apparent to me, namely, the continuity of Byzantine traditions in Western European art, even during the darkest times. He does not care much for Byzantine icons ("von der [byzantinische Schule] wir wenig Löbliches zu sagen wußten"); he sees, however, what Byzantine art has preserved, namely, the legacy of ancient art (in ihrem Innern noch für große Veredienste mit sich trug, die aus der hohen Erbschaft älterer griechischer und römischer Vorfahren kunstmäßig auf sie übergegangen, glidenmäßig aber in ihr erhalten worden), both in craft and in the portrayal of the body, which was then transmitted to Western Europe.
As I said, this connection was not something I would have noticed, not even on the example on which Goethe dwells, namely, the painting here of the Veronica cloth. Though Goethe could not have seen many works of Byzantine art -- much was carried off or destroyed during the 16th-century Iconoclasm, and surviving originals are relatively rare in northern Europe -- nevertheless medieval artists knew of them.
The Latin emperors of Constantinople, who ruled from 1204 to 1261, were a dynasty from Flanders. There was economic exchange in the 14th and 15th centuries between Flanders and Crete. Byzantine icons were given as gifts to kings, popes, nobility, and important clergy. Crusaders brought back icons.
The Serbian icon, the Holy Face of Laon, shown here at the right, was given by Pope Urban IV in 1249 to his sister Sybille, abbess of the Cistercian convent of Montreuil-en-Thiérache, France. The Vera Icon became one of the prevalent new types of painting in the West. Goethe, relying only on a work of reference, a history by Séroux d'Agincourt (containing what we today would certainly find to be inadequate plates), was able to trace this important link in the transmission.
And what about the limitations? Goethe would not have been able to appreciate such beautiful examples of medieval art as the page from the Lindisfarne Gospels at the top of this post. Aside from the fact it has no "classical" features, Goethe had no "feel" for the simple devotion and "childlike heart" (the phrase is that of E.H. Gombrich in The Story of Art), and indeed the spirituality of the early Middle Ages. It is the surface Goethe admired, the building up of elements with almost scientific accuracy, the mastery of the human body, the attainment of outer harmony.
The highest task of the visual arts is to decorate [verzieren] a specific space or to place adornment [Zierde] within an indefinite space; from this requirement derives everything that we call correct [kunstgerechte] composition. In this the Greeks and after them the Romans were great masters.
Thus everything that speaks to us as adornment must be structured [gegliedert], actually in a higher sense, that it consist of parts that relate to one another alternately. For this it is required that it have a middle, an upper and lower part, a here and a there, from which, then, symmetry arises.
From the above passage, one would like to hear Goethe's reaction to this Celtic decoration, from the Book of Kells.
The key to Goethe's distance from the spirit of early medieval art can be found in "Heidelberg," in the survey of the role of the Church, from its earliest centuries, in preserving the legacy of classical art, even if this art was against its own ethos: the Church needed to keep all the many saints and martyrs as well as the many Israelite predecessors straight! Goethe's language in writing of the "personnel," so to speak, of the new religion (dieser neue Bund) is totally anthropological and historical, with every trace of what is mysterious about the Christian revelation bracketed out. Two of my favorite locutions are "ein wundersames Kleeblatt" for the Trinity and "die vier Annalenschreiber" for the four evangelists.