The burly dark-haired man with downcast eyes in the foreground of the School of Athens draws our attention for a number of reasons.  He seems colossal in size, especially when compared with his neighbor who stands to his immediate right, holding a book in one hand while pointing out a passage to his companions with the other.  The dark-haired seated man wears a broad-yoked tunic that seems to open in the front, its shirt-tail ends parting over his knees, and plain high boots.  The other figures in the composition are shoeless or shod in sandals or^⁠ Roman soldier’s footgear, tied at mid-calf, of the type seen in the Arch of Constantine^⁠ and later engraved by Marcantonio Raimondi. The stony block that serves as the dark-haired man’s desk is turned against the prevailing orthogonal of the scene’s insistent single-point perspective.^⁠  His position seems off-kilter too: in this crisply conceived perspectival space, he does not so much sit as hover before an undefined swath of painted grey that truncates the pavement’s nested-square pattern beneath or behind his right thigh, and that lacks the top and bottom moldings seen on each riser of the scene’s wide steps.  His lack of groundedness contrasts with the weightiness of his closest neighbor, who stands with left foot firmly planted on a rough-hewn block of marble. The sole pictorial flourish in the seated man’s depiction, a small swag of drapery of uniformly purplish tones, appears to overlap the long blue-highlighted folds of his neighbor’s rose-toned, gold-edged toga painted in glorious colore cangiante.  Indeed, there is no question that the oversize brown-haired man was added to the composition late:  he does not appear in the fresco’s final preparatory drawing or cartoon, now in Milan, and in fact is painted on a piece of plaster laid in after the original smooth intonaco surface had dried.^⁠

In what Maria Loh calls “one of the best-loved stories of Renaissance art history^⁠,” this late addition is identified not only as the ancient Greek philosopher Heraclitus, but also as Michelangelo who was painting in the nearby Sistine Chapel at the very time that Raphael was painting the School of Athens in the Stanza della Segnatura.  The young Raphael was so impressed by what he saw Michelangelo painting, the story goes, that he paid homage to the older artist by inserting [in Rona Goffen’s phrase] Michelangelo’s “likeness … represented in Michelangelo’s style”^⁠ into the foreground of his first major painting for their common patron, Pope Julius II.  Loh is at pains to debunk this identification, pointing out that “this precious myth is a modern invention first proposed in 1941 by Deocleo Redig de Campos.”^⁠  based on what Loh clearly considers insufficient evidence.  Still, true or not, the story continues to circulate unrestrainedly^⁠, and many viewers today still clearly want to believe it.

Nonetheless, the question of Michelangelo’s painted presence in the School of Athens aside, the oversize and solitary figure of Heraclitus remains intriguing visually.  Here I argue that this figure’s visual dissonance within the larger composition can be productively understood if we acknowledge the seated man as the pictorial partner to Diogenes the Cynic of Sinope, who sits reading a couple of steps above.  Together these two philosophers bracket the path approached by the paired central figures of Plato and Aristotle as they walk together towards the painted hall’s foreground.  While Plato and Aristotle actively debate their respective points of view, the former pointing upwards towards an unseen ideal while the latter gestures down towards the earth’s essential materiality, Heraclitus and Diogenes are each more isolated from the convivial debates taking place around them, the two mirroring one another in their solitude.  One figure’s pose inverts the other’s: Heraclitus’ bent limbs curl inwards towards his torso, whereas Diogenes’ splayed legs and supporting left elbow open up Heraclitus’ inward turn.  The ink pot at Heraclitus coiled left elbow teeters pictorially off the back corner of the carved block that serves as his desk, finally resting on the very step that, farther to the right, also bears Diogenes’ cup.

The two figures’ activities are linked too. Heraclitus writes, left hand lifted to support his downturned head while, beneath the quill in his right hand, the top right corner of his paper curls upwards.  He does not look at what he writes, perhaps demonstrating his distrust of sight as a source of knowledge.^⁠  The opening passage in the first letter fragment “to Heraclitus” published by Aldus Manutius in 1499 in Epistolarum Graecarum Collectio aptly describes as finished his task in the fresco:  “You have written down a discourse…that is hard to understand.”  Though we literally cannot read what the painted Heraclitus has written, the hanging indentation of the lines suggests the beginning of a sonnet—a stanza^⁠ in progress, to use the Italian word for both “room” and “part of a poem.”  In contrast to Heraclitus, Diogenes of Sinope has neither pen nor ink pot.  He does not write.  Instead Diogenes reads, left hand extended to hold a folded sheet up for his farsighted gaze.

Tracng the “multiple portraits of Renaissance letters read, delivered, and transported” in Mantegna’s Camera Picta, Paula Findlen characterizes the letter motif as “a skein unwinding across different scenes of encounter, binding them together.” In contrast, Shira Brisman^⁠ emphasizes the social distancing that a letter represents, arguing that such paper correspondence is “a written communication sent from an author to a recipient traveling across a geographical divide and gaining temporal distance before it is delivered.”  While I do not argue that in Raphael’s fresco Diogenes is reading exactly what Heraclitus writes, I am suggesting that their parallel activities —one initiating what Brisman calls “an epistolary mode of address,” and the other receiving such an interpellation—draw our attention both to the binding ties a successfully received letter can generate and the aching ruptures that can arise when an intended transmission fails to reach a recipient.

Needless to say, Renaissance humanist culture was well acquainted with both triumphant rediscoveries of classical learning and a keen awareness of the many lost achievements by authors and artists from long ago.  Raphael’s Stanza della Segnatura itself, as Pope Julius II’s private library, was the site for conserving and consulting texts from many centuries, including some portrayed in the room’s frescoes^⁠.  Furthermore, as Alex Nagel and Chris Wood have demonstrated, the Stanza della Segnatura thematizes “the paradox of inscription, described by Plato in the Phaedrus, whereby writing compensates for an imperfect, distorting human memory but only at the price of a vertiginous loss of confidence in the referential authority of the verbal text.”^⁠  The split pairing of Heraclitus and Diogenes in the foreground of Raphael’s School of Athens further vexes that paradox:  if a written text could preserve the spoken word, it might also fail to do so.

In the Renaissance (as now), there were no complete surviving works by either Heraclitus or Diogenes.  They were known largely through their respective biographies in the much-read Lives of Eminent Philosophers by Diogenes Laertius from the early third century CE, the comments and responses of later philosophers including Plato, and fragments attributed to them of the type published by Aldus Manutius in 1499.^⁠  In the School of Athens, other scholars are shown with a bound book or codex, a scroll or a slate.  In contrast, Heraclitus and Diogenes each has a loose sheet of paper.  Such single sheets of paper are fragile, far more vulnerable to damage or loss than a book’s protected pages.  These loose leaves, fragments of a lost larger corpus, in the hands of two lone thinkers isolated within a sociable company of philosophers remind us that the promise of permanence that writing holds out is sometimes broken…