Beryllus lapis est lucidus, albus et transparens. Cui datur forma concava pariter et convexa, et per ipsum, videns attingit prius invisible. Intellectualibus oculis si intellectualis beryllus, qui formam habeat maximam pariter et minimam, adaptur, per eius medium attingitus indivisibile omnium principum.

The beryl is a brilliant, white and transparent stone. It is possessed simultaneously of a concave and a convex form, and whoever attempts to peer through it comes across things hitherto invisible. If we measure a beryl to reason and fix the gaze of eyes of reason upon it, we perceive the greatest and the smallest forms at once and are thus affected by the recognition of the inseparable origins of the all.

–Niclas Krebs, later Cardinal Nicholas of Kues, De beryllo, cap. ii (1458) in Nikolaus von Kues’ philosophisch-theologische Werke in deutscher und lateinischer Sprache, vol. 3, p. 4 (S.H. transl.)

Scientia brevissima est, says the master, quæ sine omni scriptura melius communicaretur, si essent petentes atque dispositi. True wisdom requires few words, and indeed would best be imparted entirely without writing, when the time arrives that people have the capacity so to consume it. Jan van Eyck conveys his message without words. That his message includes wisdom goes without saying. But it is an irony of our day that critical aspects of his message go unnoticed, forgotten, misremembered. Today science has brought us wealth and creature comforts, it gives us a life beyond the harsh struggle for subsistence. Leisure is a common attainment of humankind. But are we truly wiser than our forebears? Certainly the day that Cusanus imagines, when the human species advances to a form of communication in images, beyond speech and writing, has not yet reached us–though through the attainments of science, it may in fact be drawing near.

The double portrait of Giovanni Arnolfini, the wealthy merchant of Lucca, who ended his days a knight in the service of Philip the Good of Burgundy, and his wife, Jeanne Cenami, is the stuff of undergraduate art history examinations. Is this a painting to mark their wedding? But where is the priest? Is Jeanne pregnant or merely wearing a fashionable gown? Why is there a single lit candle in the chandelier, and that by broad daylight? (Erwin Panofsky, teaching that the Arnolfini double portrait stands at the threshold between secular and sacred art, answers all those questions in volume one of Early Netherlandish Paintings–though later scholars have disputed some of his conclusions). But I want to focus on one simple feature of this painting, easily overlooked, though essential to its meaning: the bull’s-eye mirror.

The Arnolfini double portrait is marked by firm geometrical principles, and the mirror is found between the portrait subjects, at the painting’s vanishing point. A gilded frame features ten rosettes, each with a carved scene from the passion of Christ, and immediately to the left are two sets of rosary beads, reminding us of the devotional purpose of these images. The Arnolfinis are a pious couple, it tells us. They launch their new life together conscious of the teachings of Christ at Cana. But what about that mirror? Can it not symbolize wealth, vanity, frivolity? Not this mirror. It is a speculum sine macula, a mirror without a blemish (from Wisdom 7:26, taken by Christians later as an emblem of Marian devotion). In the convex eye of the mirror, the oculus dei, the dimensions of the portrait are exploded. We see the space before the Arnolfini couple; the door has opened and the painter, Jan van Eyck, has entered, arrayed in a blue robe and wearing a turban configured much in the manner like one of van Eyck’s famous self-portraits. What an act of whimsy or humor for him to write, just above his own portrait in miniature, on the wall, the line associated with generations of Kilroys: Johannes de Eyck fuit hic — Jan van Eyck was here. He is accompanied by another unidentified figure. And we see other details of the room, as well as the backs of the portrait figures. What is the purpose of this detail, so meticulously rendered? The room’s details seem modest to the current viewer, but for their times they signal wealth and power, much as Arnolfini’s luxurious dark purple fur-trimmed robes do; key signals tell us that the owner is a religious man. The mirror allows the painter to give us a three-dimensional sense, an additional depth perception beyond that furnished by the carefully studied and executed perspective. But I suspect that for van Eyck there is still another, deeper meaning associated with that lens. The explanation comes, as in so many of the van Eyck paintings, from his rough contemporary, Cusanus.

In his scientific-theological tractate De beryllo (On the Beryl), Cusanus leads with a discussion of the properties of crystals naturally occuring in nature, and then he comes to a discussion of the special properties of the convex and concave forms and their theological significance. They permit the viewer who knows how to apply them to gain special insights, to plow into the secrets of the tiniest forms and the mysteries of the cosmos above and about us. Homo est mensura rerum, he writes–the human is the measure of all things; measure, and measurer. And the beryl (i.e., not a gemstone, but a specially crafted lens), is a means to measure and appreciate what is beneath and above, but also that which is inside the individual. Attente considera per beryllum ad indivisible pertingi–by means of the beryl you may yet achieve the indivisible. He means this in a scientific sense, namely that we will be able to perceive things which human eyes cannot see; but more significantly, he points to a thread which connects all things and which reflects a great design in the world of our immediate perception, just as it does in the subatomic worlds and in the cosmos. Finally, he focuses on the properties of the mirror and the need for human introspection: study well what is above and below you, but do not forget to come to an understanding of yourself.

Look into van Eyck’s mirror, and you may yet see all the things that Cusanus suggests may be seen and understood. It points to a universe within to match the one outside us. Which explains why it must be set at the vanishing point, with the artist’s own image set at the center.