HERCULES SLAYING CACUS IN THE HYPOGEUM OF THE VIA DINO COMPAGNI, ROME

Abstract

Considering Roman art as a cumulative process could help resolve a small iconographical problem. Cubiculum N in the burial hypogeum under the Via Dino Compagni in Rome (c.350–75 ce) features a series of figure scenes referencing the exploits of the mythological hero Hercules. One of these scenes, presently entitled Hercules Slaying an Unknown Enemy, has no direct equivalent in extant Roman art and so has proved difficult to identify. This article suggests that Hercules’ battle with Cacus is most likely the incident referred to here. This is because Antonine medallions and coins, and third-century Roman sarcophagi, use imagery associated with the Cacus story that collectively could have contributed to the design of the Unknown Enemy panel. Further, identifying the defeated enemy as Cacus fits in with, and indeed helps to clarify, programmatic themes and associations already established in the other figure scenes in this funerary chamber.

Approaches to ancient Roman art have changed in recent years. In trying to understand Roman imagery, reliance is no longer placed on ancient texts only, although such texts have of course remained a useful source. Pioneering scholars such as Tonio Hölscher have pointed out that Roman art is not just the personal expression of artists and patrons but is also ‘a factor in the collective life of a society’, the product of shared cultural knowledge.¹ Accordingly, more wide-ranging methodologies for ‘reading’ visual images have been developed in art historical and archaeological circles, and these have been augmented by methodologies used in new disciplines such as sociology and anthropology.² This article adopts such an art historical/archaeological approach, starting with close observation of the art object itself to see what can be learned from this, and then widening the scope of study to consider social and cultural contexts, including literary contexts, which may have a bearing on the iconography.

It also needs to be noted that in general Roman artworks did not correspond to modern concepts of ‘creative art’; that is, Roman artists and craftsmen did not place the same emphasis on originality and individuality as is the case today.³ Further, while it has long been presumed that the tendency towards replication in Roman art involved mainly copying lost Greek masterpieces, a more nuanced approach to this question of Kopienkritik is now preferred. Roman iconography seems rather to have developed incrementally, almost communally, over time, continually adapting currently available ‘stock types’ under the influence of prevailing social and cultural mores.⁴ The new, more varied imagery that arises from this eclecticism has a cumulative effect and is necessarily multivalent, drawing from viewers a range of preconceived associations and open to change according to context. While such a process might simply reflect a solution to a formal problem, it also gives rise to thematic correspondences and contrasts; indeed, on occasion adjustments to iconography may have been made precisely to achieve some kind of programmatic statement.⁵

It will be suggested here that this kind of cumulative approach can be detected in, and help resolve, a hitherto unidentified Hercules image in the fourth-century burial hypogeum on the Via Dino Compagni in Rome (formerly known as the New Catacomb of the Via Latina).⁶ Cubiculum N in this hypogeum (c.350–75 ce) is situated amongst other cubicula featuring biblical scenes but in itself has no specifically Christian iconography or inscriptions. The figure scenes in this cubiculum feature instead Alcestis and the mythological hero Hercules (Figure 1). These scenes are arranged in two sets of three, each set comprising a central lunette flanked by pendent panels, and each set decorating a double arcosolium which faces the other one on the opposite side of the room. In the lunette on the left-hand, western side, Alcestis tends Admetus as he lies ill, offering to die instead of him, while opposite, in a matching lunette on the eastern side, Hercules and Cerberus return Alcestis from the Underworld to Admetus, alive and well.⁷ The four rectangular panels that flank these lunettes, two at each end of the room, refer to other Herculean exploits: Hercules slaying the Lernaean Hydra and standing in the Garden of the Hesperides on the right side, and on the left side Hercules joining hands with the goddess Minerva and slaying another enemy.

Figure 1. Figure scenes in cubiculum N: A. Alcestis tending Admetus as he lies ill; B. Hercules and Cerberus returning Alcestis to Admetus; C. Hercules slaying an unknown enemy; D. Hercules slaying the Lernaean Hydra; E. Hercules and Minerva; F. Hercules in the Garden of the Hesperides. Diagram compiled by J. Mill.

Most of the figure scenes in this chamber are readily recognizable, and it has been shown that they are based mainly on traditional Roman iconography, especially that found in funerary contexts and on imperial coinage, and further that these scenes may reference traditional Roman values suitable in a funerary context.⁸ One panel, however, has no direct equivalent in extant Roman art and has been difficult to identify (see Figure 1C; Figure 2). In this scene, to the right of the western arcosolium, Hercules stands frontally, his weight on his left leg with his right leg bent at the knee in a slight contrapposto pose. He is bearded, has a blue halo, and his lion-skin is draped over his left shoulder and upper arm, to hang down behind him and beside his right and left legs. His club in his right hand is raised behind his head, ready to strike. Propped up to the right of the scene are his other weapons: a large bow and quiver with arrows. With his left hand, Hercules holds up the limp right arm of a naked, apparently dying man who lies stretched out on the ground at his feet. This man has yellowish skin, and, leaning on his left side, turns his head towards the viewer. The identity of this dying figure has not yet been determined, and Ferrua, Elsner, Zimmermann, and Tatham chose to call him simply an anonymous ‘human enemy’.⁹

Figure 2. Hercules slaying an unknown enemy. Rome, hypogeum at Via Dino Compagni, cubiculum N, in situ (c.250–75 ce). Photo courtesy of Pontifical Commission for Sacred Archaeology.

Naturally, attempts have been made to identify this vanquished enemy; the main suggestions have been Geryon, Antaeus, Alcyoneus, Cacus, and Death.¹⁰ To date none of these suggestions has gained wide acceptance, and full consensus has yet to be reached. This is at least in part because the Roman iconography conventionally associated with these entities does not correlate closely enough with the scene in cubiculum N, where Hercules stands over a man lying on the ground and links hands with someone in the scene. Geryon is a popular figure, but when fighting Hercules he is normally depicted with three heads and wearing armour.¹¹ Antaeus appears on Roman coins and occasionally on sarcophagi, but the iconography shows Hercules and Antaeus both upright, Hercules holding Antaeus by the waist and lifting him off the ground.¹² In Greek art, Alcyoneus is depicted lying asleep on the ground as Herakles sneaks up on him, but this scene is not a feature of Roman art. Again, Death (Thanatos) as a personification with wings appears in Greek, but seemingly not in Roman art.¹³

On the other hand, there are Roman images referencing Hercules’ defeat of Cacus, which do show similarities with the panel under discussion. Accordingly, this article seeks to reopen the question, and suggests that Cacus is most likely the victim represented in this scene.

Frederick Perez Bargebuhr, in the course of arguing for a Christian interpretation of the Hercules scenes in cubiculum N, seems to have been the first to consider that ‘the troglodyte Cacus who inhabited the Aventine Hill of the future city of Rome’ might be the enemy depicted in this panel.¹⁴ Writing originally in the 1960s, he pointed out that the dying figure in this scene has only one head and so, contra Marcel Simon, is clearly not the triple-headed Geryon of Hercules’ tenth labour. Instead, Bargebuhr supported his own suggestion by quoting extensively from Augustan literary sources: Livy 1.7.3–15; Virgil, Aeneid 8.185–275; Propertius 4.9.1–20; and Ovid, Fasti 1.543–87, 643–52.¹⁵ While details differ, these passages all tell the story of Hercules’ arrival at the site where Rome will be built, leading the herd of cattle he has taken from Geryon. While Hercules sleeps beside the Tiber, some of this herd are stolen by Cacus, son of Vulcan, who lives in a cavern and terrorizes the local inhabitants. In a mighty battle, Hercules kills the thief, recovers his cattle, and in doing so makes the area safe for the people who live there. In return, marking the institution of rites commemorating the hero's contribution to the founding of Rome, a shrine and an altar, the Ara Maxima, are established in honour of Hercules Victor (or Invictus) at what would become the Forum Boarium, the cattle market in Rome.¹⁶ In many ways, the story of the victory over Cacus, with its emphasis on cattle theft, mirrors the Geryon story and is clearly an aetion (‘causative myth’) for Roman readers, explaining Hercules’ connection with the area and the cult practices at the Ara Maxima Herculis Invicti.

In support of his Cacus proposal, as it has been left to us, Bargebuhr cites only those four Augustan literary sources with little explanatory comment, and he takes his argument no further. His book, The Paintings of the ‘New’ Catacomb of the Via Latina and the Struggle of Christianity against Paganism, was edited and published posthumously; it was clearly unfinished, and his main thesis now seems dated.¹⁷ There is, however, more that can be said in favour of his suggestion that Cacus may be the enemy intended in cubiculum N.

Contextually, in Rome one might expect to find Cacus alongside depictions of Hercules’ other exploits. This is because, while the well-known labours represent Hercules travelling around the known world and beyond, in Roman literature it is the story of Geryon and the pendent story of Cacus that became popular, explaining Hercules’ presence in Italy and in the environs of Rome in particular. As we have seen, the tale acts as a prelude to the dedication of the Ara Maxima at the supposed site of the battle, and offers a way of uniting diverse, and potentially contradictory, topographical lore.¹⁸ All in all, it seems to be a local story.

While the monstrous, fire-belching, cattle-thieving Cacus of Virgil's Book 8 has taken hold in our imagination, this is not the only form by which Cacus was known in pre-Roman and Roman mythology. On an Etruscan mirror from Bolsena (c.300–200 bce), now in the collection of the British Museum, ‘Cacu’, identified by inscription, is represented as an Apollonian figure playing a lyre; this human Cacu also appears on late Etruscan funerary urns (second century bce).¹⁹ Jocelyn Penny Small, in her Cacus and Marsyas in Etrusco-Roman Legend, traces the evolution of Etruscan Cacu to Roman Cacus, noting the earliest surviving literary versions of Cacus’ presence in the Hercules legend, as recorded by L. Cassius Hemina and Gnaeus Gellius in the second century bce.²⁰ These writers portray Cacus as very much human.

The association with monstrousness seems to arise from a false etymology to which Servius later lends his authority (ad Aen. 8.190), connecting the Etruscan name Cacu with the Greek term κακός (kakos, bad).²¹ In the Augustan period both the human and the ogre Cacus co-exist: historians Livy and Dionysius of Halicarnassus depict Cacus as human, while, following Virgil, the apparent originator of the half-monster trope, poets Propertius and Ovid depict Cacus as monstrous. The monstrousness might have been enhanced by strata of local folklore overlying the Etruscan original. Dana Sutton points out that the Cacus myth shares many characteristics with the kinds of stories used in Greek satyr plays and/or Atellan farce, and suggests a derivation from a similar story involving Sisyphus, possibly used in these comic plays.²² Small suggests that the transformation was Augustan propaganda, part of a process of bringing all oracles and auguries under the personal authority of the princeps.²³

At any rate, in the second century ce, under the Antonines, there was a revival of interest in the Cacus story, as part of a general emphasis on Roman tradition and a return to the romanticized nostalgia of the Augustan age. Reflecting the Zeitgeist, a series of medallions from the imperial mint in Rome has on their reverse scenes illustrating episodes from the legendary history of Rome, including references to Romulus and Remus, Aeneas, the Sabine women, and the institution of the cults of Hercules, Aesculapius, and Cybele.²⁴ The medallions in this series are of high quality, and show awareness of literary sources such as Livy, Virgil, and Ovid, as well as of related iconography used in art; they may have been gifts from the emperor, intended for an elite, educated sector of society.

For our purposes, one of these commemorative medallions, issued by Antoninus Pius in 140–3 ce, depicts on the reverse Hercules as the slayer of Cacus and so the founder of Hercules’ cult in Rome (Figure 3).²⁵ Hercules stands in the middle of this scene, hierarchically larger than the other figures, frontal but turning slightly towards the viewer's left. He is bearded and naked, with the lion-skin slung over his left shoulder and arm to hang down his left side, the lion's head and forepaws clearly visible. In Hercules’ outstretched right hand, he holds his lowered club, indicating that the battle is over. Behind the hero is a large rocky crag with a tree, and at the foot of this rock a dead man, Cacus. He lies on his back, with only his naked upper torso visible, presumably at the entrance to his cave. His face is twisted back towards the viewer. Left of Hercules are four smaller men in short tunics, the grateful local inhabitants; the man in front reaches out to kiss Hercules’ outstretched right hand. This is currently considered the only certain visual representation of Cacus in extant Roman art,²⁶ but we can deduce from this at least that the pictorial tradition retained the human form of the ogre and that at this stage the iconography involved the dead body of Cacus lying on the ground beside the victorious Hercules. We also note the detail whereby Hercules reaches out and links hands with another figure in the scene.

Figure 3. Hercules being thanked after killing Cacus. Reverse of a bronze medallion of Antoninus Pius (140–43 ce). Engraving by Ridolfino Venuti, in S. W. Stevenson, C. R. Smith and F. W. Madden, A Dictionary of Roman Coins (London, 1889), 455.

A similar bronze medallion, but without the grateful populace, was ostensibly issued by Marcus Aurelius (perhaps 147 ce).²⁷ The reverse has, simply, Hercules standing beardless and naked, his weight on his left leg. He holds his lowered club in his right hand and apples behind his back in his left. There is a large rock in low relief to the right, with, again, the naked upper body of the dead Cacus lying on his back, his lower body concealed by the rock. Here, Cacus also takes human form. Unfortunately, although accepted as genuine by Gnecchi, Münzer, Vermeule, and others, the authenticity of this medallion has been questioned.²⁸

This numismatic Cacus type, Hercules triumphant over the supine Cacus, seems to have been adapted from received iconography that portrayed Theseus being thanked after rescuing the Athenians from the Minotaur. Paintings from Pompeii and Herculaneum show Theseus heroically nude, with his cape over his left shoulder and upper arm and his narrow club resting against his left upper arm (Figure 4).²⁹ He stands in a slight contrapposto pose, with his weight on his left leg and his right leg bent at the knee. He is flanked by grateful Athenians, one of whom kisses his right hand while another crouches at his left foot. The defeated Minotaur lies dead on his back on the ground behind him, his head twisted towards the viewer and his lower body disappearing into the doorway to the labyrinth. By this time, Theseus seems to have been regarded as a kind of secondary Hercules, and his club and cape in these scenes resemble familiar Herculean attributes.³⁰ This sort of scene could well have been regarded as a suitable source for the Cacus image on the Antonine medallion, reinforcing the concept of a civic hero defeating a monster and restoring justice and peace to grateful citizens. In any case, clearly by the second century ce an iconography had already evolved whereby a Hercules-like figure with a club could be represented as standing triumphantly over a dead body on the ground, while extending his hand to another figure.³¹

Figure 4. Theseus honoured by the Athenians after killing the Minotaur (first century ce). Wall painting from the Casa di Gavius Rufus, Pompeii. Naples, National Archaeological Museum, inv. 9043. Public domain via Wikimedia Commons (photo M.-L. Nguyen).

Contemporaneous with the Cacus medallion(s), a more widely distributed Antonine numismatic type also referenced the Cacus story as aetion, although omitting actual depiction of Cacus himself and focusing instead on Hercules and the Ara Maxima. This type, issued as a medallion under Marcus Aurelius, Lucius Verus, and Commodus, shows on the reverse Hercules after the defeat of Cacus, crowning himself victor in a grove beside the Ara Maxima.³² A typical example, a bronze medallion issued by Lucius Verus (165 ce), has in the centre a young, naked, beardless Hercules facing the viewer, his right hand raised in the act of placing a victory wreath on his own head; his club rests on his left arm, along with the lion-skin, which hangs down alongside his left leg (Figure 5).³³ Hercules rests his weight on his left foot, with his right leg slightly bent at the knee; that is, he adopts the familiar slight contrapposto stance. On the left, representing the sacred grove, is a tree with Hercules’ bow and quiver hanging from a branch; on the right is a garlanded square altar, the Ara Maxima, with flames burning on top. This Hercules-crowning-himself type seems to have been well known in Rome. There was a statue of Hercules adopting this pose at the entrance to the Temple of Concordia on the Capitoline Hill,³⁴ and this Ara Maxima scene was repeated on Caracalla's coinage (198–217 ce), followed by still later numismatic examples up until about 295 ce.³⁵

Figure 5. Hercules crowning himself at the Ara Maxima. Reverse of a bronze medallion issued by Lucius Verus (165 ce). Paris, Bibliothèque Nationale de France. Reproduced from Gnecchi (1912), pl. 77.1 (n. 25).

The Antonine commemorative series, of which these Hercules/Cacus scenes formed part, was much admired and influential; the medallions and coins were collected and copied well into the fourth century.³⁶ As Clare Rowan has pointed out, ‘once struck, such images entered the broader Roman visual language’.³⁷

A detailed examination of these [Antonine] medallions reveals that their iconography was drawn from earlier types, and that they in turn inspired later imagery. This phenomenon reveals a certain intertextuality in numismatic language and suggests that coin imagery did not merely grace Rome's currency but was recorded and accessible to later generations.³⁸

By the third century ce, the Hercules-crowning-himself type also finds its way into relief sculpture on Roman sarcophagi, where a series documented by Peter F. B. Jongste features the twelve labours of Hercules (second–third centuries ce).³⁹ On these sarcophagi, the crowning-himself image is modified to depict Hercules with the dead Nemean lion; the Cacus incident, of course, was not one of the traditional twelve labours. So, for instance, a sarcophagus from the mid-third century shows the hero, naked and beardless, in the conventional contrapposto pose, although here with his weight on his right leg.⁴⁰ He now wears the triumphal wreath on his head, so that his upraised right arm can wield his club to indicate ongoing aggression. Beside him, as on the coins, is a tree from which hang his bow and a quiver with arrows. Rather than standing over a human body, however, the left hand of Hercules holds the dead Nemean lion by the left rear paw as it lies on the ground beside him.⁴¹ Except that the dead body is a lion rather than a human, this scene is very like the unknown enemy one in cubiculum N.

Indeed, the Antonine Hercules/Cacus medallions, the third-century labours-of-Hercules sarcophagi, and the panel under discussion in cubiculum N have many details in common. In cubiculum N, as on the Antoninus Pius medallion, Hercules stands beside a dead or dying human enemy who lies on the ground near his feet; Hercules’ left side is the same as on this medallion, with the lion-skin thrown over his shoulder and upper arm, the lion's face and fore paws hanging down at his left side. He stands frontally with a slight contrapposto turn, his weight on his left foot and his more relaxed right leg bent at the knee.⁴² Moreover, in both the medallion and the panel, Hercules extends an arm to join hands with another figure in the scene. In the panel, though, as on the sarcophagi, he turns to his left instead of his right and extends his left hand rather than his right as he holds the limb of his vanquished enemy; the right-handed ‘handshake’ gesture occurs with Minerva in the panel opposite instead. As on the sarcophagi, Hercules’ right arm is raised, not to crown himself, but to hold up his club ready to strike. While in cubiculum N the grateful citizens, landscape details, altar, and tree have all been dispensed with, it is notable that Hercules’ bow and quiver remain, thus perhaps helping to identify the scene. Despite differences, then, there are enough similarities in this eclectic mix to suggest that, when devising the panel in cubiculum N, the figure painter(s) had Cacus imagery in mind. It also seems likely that, while modern scholars find the ‘unknown enemy’ scene in cubiculum N difficult to identify, viewers in Late Antiquity could have found the image and its attendant concepts recognizable enough.

The modifications imposed in the putative Cacus painting seem to have arisen from a desire to accommodate conceptual patterns established elsewhere in cubiculum N.⁴³ In particular, we may note the complex compositional mirroring in the various facing images (see Figure 1). The rectangular panels flanking the eastern arcosolium have the Hercules figures each confronting a large serpentine enemy; formally, the shape of the Hydra, with its coiling trunk-like body surmounted by branched heads, is mirrored in the tree with the serpent Ladon opposite. Meanwhile, in the western arcosolium the pendent panels, apparently deliberately, reference human figures rather than strange creatures, and are connected by the visual cue of joined hands, this gesture strategically placed near the centre of each scene.

On the left-hand side of the eastern arcosolium, Hercules has his club raised to slay the Lernaean Hydra, in effect the mortal man of action, while opposite is an image of the contemplative, divine Hercules, club lowered, retrieving the golden apples of the Hesperides.⁴⁴ A similar antithesis can be found in the images at the other end of the cubiculum. On the wall to the left of the lunette, standing beside Minerva, Hercules is a calm divine being, club pointing downward, the auspicious dextrarum iunctio (joining of right hands) gesture denoting concordia (harmony, like-mindedness, good will) between Hercules and his patron goddess. In Graeco-Roman culture, this ‘handshake’ gesture is associated with images of gods greeting earthly rulers, as well as with allegories of political diplomacy and the deceased with their spouses.⁴⁵ On coins the gesture is often explained by the inscription concordia, and marriage scenes featuring the gesture on sarcophagi may be accompanied by the personification of Concordia herself.

Opposite, in the possible Cacus scene, Hercules is again the mortal man of action in a vigorous posture, club raised; rather than denoting goodwill, his aggressive pose and his clutching of his slain enemy with his left hand suggest disharmony and disruption. Research into Roman attitudes towards left and right has so far proved complex and inconclusive, but in Roman art at least there seems to be a convention whereby, as with Hercules here, killers/victors hold a limb of their dead victim in their left hand. Hercules holds the dead Nemean lion in this way on a medallion issued by Commodus (192 ce) and on the labours-of-Hercules sarcophagi discussed above.⁴⁶ An example also occurs in a sculptural type where the seated Polyphemus casually holds in his left hand the arm of a dead sailor lying at his feet.⁴⁷ One instance of this type, a heavily restored marble statue in the Capitoline Museum in Rome (c.138–80 ce), has the dead body lying along the ground at the Cyclops’ feet in a posture very like that in our ‘unknown enemy’ scene.⁴⁸ On second-century ce mythological sarcophagi, Medea holds the leg of her dead child in her left hand, slung over her shoulder; similarly, a fragmentary statue group from the Baths of Caracalla (early third century ce) has a striding Achilles holding in his left hand the body of Troilus, also slung over his shoulder.⁴⁹ All told, unlike the right-handed ‘handshake’, this left-handed grasp looks like a dismissive or contemptuous gesture.

If the ‘unknown enemy’ is Cacus, interesting implications arise. Cacus’ name fits conveniently with the fact that Hercules was known by the epithet Alexicacus (Greek Ἀλεξίκακος, Alexikakos, Averter of Evil), so from this perspective, in defeating Cacus, Hercules is confounding ‘badness’/evil itself.⁵⁰ If this scene in cubiculum N is intended to represent the rejection of vice, then it is appropriate that the facing scene has Hercules allied with the goddess Minerva, since Minerva seems at times to have been thought of as embodying virtus (manly excellence), the prime Roman virtue and clearly the opposite of vice. This virtuous Minerva is found, for instance, on an antoninianus of Claudius II Gothicus (268–70 ce), where, on the reverse, Minerva stands in her long tunic with helmet, shield, and spear, alongside the inscription VIRTUS AUG[usti] (the virtue of Augustus).⁵¹ The first excavator of the Via Dino Compagni hypogeum, Antonio Ferrua, pointed out this connotation from the outset, labelling the Minerva scene ‘The Choice of Hercules’ in reference to the sophist Prodicus’ famous story about Hercules at the crossroads, choosing virtue over vice (Xen., Mem. 2.1.21–34; Cic., Off. 1.18; cf. 3.25).⁵² An emphasis on moralism in the Cacus and Minerva panels in cubiculum N would fit with the other figure scenes in cubiculum N, which have connections with coins inscribed with qualities such as virtus and pietas (dutiful respect).⁵³

The story of Hercules’ choice was a popular one, widely known, and often used allusively. Silius Italicus gave Scipio Africanus the Ciceronian choice between virtus and voluptas (bodily pleasure), the latter described as the ‘the enemy of Virtue’⁵⁴ (Pun. 15.18–128). Widening the options, Dio Chrysostom's advice to Trajan on kingship offers a choice between royalty or tyranny (Or. 1.52–84), while Lucian has his younger self choosing between education or sculpture (Somn. 6–9). Contemporary with the decoration in cubiculum N, the apostate emperor Julian casts himself as Hercules in his quest to restore pagan religion and considers whether to choose the virtuous or the easy way (Or. 7.229c–34c)⁵⁵; writing in support of this quest, Libanius also portrays Julian as Hercules (Or. 13.47; 15.36) and has him similarly considering Prodicus’ choice (Or. 12).

Prodicus’ parable was an important touchstone for the Stoics, and for Romans in general, providing an exemplum whereby Hercules as the ideal sapiens (wise man, sage) chooses arete or virtue and refuses the blandishments of kakia (recalling the false etymology of Cacus) or vice.⁵⁶ To the Stoic imagination, the story of Hercules defeating Cacus, who embodies the qualities disparaged in Seneca's De ira, lends itself as an allegory for the triumph of Stoic virtue over the passions and bestial aspect of the human. Theodore Antoniadis makes a case for this being a recurring Stoic paradigm in Roman literature, grouping Cacus with other similarly barbaric foes such as the Cyclops Polyphemus in Ovid's Metamorphoses and Amycus in Valerius Flaccus’ Argonautica.⁵⁷ Roman Stoicism assimilated the traditional values of the mos maiorum (the customs of the ancestors) largely uninflected, and Hercules was for Romans in general an archetype not only of virtus, but also of values such as fides (loyalty), pietas, and dignitas (dignity).

Christians also came to espouse this Stoic ideal, often combining the Cacus story with the Choice story.⁵⁸ Justin Martyr (100–165 ce; 2 Apol. 11.3–6) and Basil, Bishop of Caesarea (c.370s ce; Address to Young Men on How to Read Greek Literature 5.55–77), approve the moral sentiments underlying the essentially pagan account of Hercules’ choice.⁵⁹ At a critical stage in his life, Augustine portrays his own Herculean choice as that between chastity and carnality (397–400 ce; Conf. 8.11.26–8).⁶⁰ Prudentius, in his Psychomachia (early fifth century ce) uses the Hercules and Cacus account as a model for his allegorical battle between various personifications of virtue and vice; indeed, one of his pairs of combatants involves Concordia and Discordia. Later, Fulgentius approves the story of Hercules and Cacus as a form of Christian allegory, expressly designating Hercules as Virtue and Cacus as Vice (fl. late fifth/early sixth centuries ce; Myth. 2.3), while Boethius includes the Cacus story among Hercules’ twelve labours, which he sees as a parallel for the moral struggle of the sage (523 ce; On the Consolation of Philosophy 4.13–35).

If the ‘unknown enemy’ in cubiculum N is Cacus/vice and the Minerva panel refers to Hercules’ choice of virtue at the crossroads, then all the figure scenes in cubiculum N are patently narrative scenes; that is, they illustrate well-known stories about Hercules, showing the hero in a positive light. This is an approach reminiscent of the earlier labours-of-Hercules sarcophagi, where the series of Herculean labours is thought to represent the deceased's idealized journey through life.⁶¹ Kampen, Zanker, Newby, and others have argued that, in a burial context, mythological imagery like this can stand for the kind of conventional praise and consolation found in traditional funerary eulogy, demonstrating that the deceased and their family are aware of, and acting properly in accordance with, Roman social ideals.⁶² The respective eulogies of the pagan Praetextatus and his wife Paulina, inscribed for each other on altars in Rome (c.384–7 ce), show that these funerary conventions survived well into Late Antiquity.⁶³ Whatever else may be read into the imagery in cubiculum N, then, at the very least the stories represented there reflect traditional Roman values, particularly in relation to virtus. The potential for antithesis in the Cacus and Minerva imagery helps to make these sentiments clear.

To sum up, the ‘unknown enemy’ scene in cubiculum N shows affinities with earlier Roman imagery that references not only the triumphant Hercules but more specifically the defeat of Cacus and the institution of Hercules’ cult in Rome. That is, while the scenes on the Antonine medallions and third-century labours-of-Hercules sarcophagi are not exactly like the unknown enemy scene, their combined imagery correlates closely with the iconography used in the ‘unknown enemy’ panel and could have influenced the design of this scene. In addition, identifying the defeated enemy as Cacus/vice allows a possible reference in the western pendent panels to Prodicus’ moralistic tale of Hercules choosing the more worthy path of virtue. Such a reading would suit programmatic themes and associations already established in the other figure scenes in the room, which similarly seem to reference conventional Roman values. Accordingly, considering the ‘unknown enemy’ to be Cacus helps to provide a coherent memorial for the deceased in the chamber as a whole, creating an eclectic visual epitaph that suits the funerary setting.