The Baths of Trajan Decius — or of Philip the Arab?

The antiquarian and artist Pirro Ligorio (c. 1513-1583) has left us a tantalizing reference that may cast some light on the shady circumstances surrounding the completion of the Baths of Decius. In his Libro . . . delle antichità di Roma (1553) Pirro wrote:

. . . ma Spartiano dice che Decio Traiano Imperatore ristaurà le Therme di Agrippa senze far mentione, che egli ne edificasse de nuove, le quali se pur egli havesse edificate. . .

. . . but Spartianus says that the emperor Trajan Decius restored the Baths of Agrippa without mentioning that he had not built them from the ground up, as if he [Decius] had really built them himself . . .⁷³

This text is problematic in several ways. The source to whom Pirro refers is “Aelius Spartianus,” one of the pseudonyms used by the author of the Historia Augusta, a collection of biographies of Roman emperors composed in the late 4th c.⁷⁴ The text of the Historia Augusta has come down to us incomplete: there is a lacuna from the reign of Philip until the end of the reign of Valerian, that is, from about 244 to 260. This lacuna is due to a physical loss in transmission; the original text undoubtedly contained the biographies of the missing emperors, including that of Decius.⁷⁵ The Historia Augusta biographies are a mixed bag, some providing authentic information that can be confirmed from other sources, others consisting mostly of fiction. The lost biography of Decius was probably one of the more reliable sort if, as Timothy Barnes has argued, the author’s primary source for the period was the 3rd-c. Greek historian P. Herennius Dexippus.⁷⁶

In the surviving portion of the Historia Augusta the accounts of the reigns from the Philippi to Claudius Gothicus are credited not to “Aelius Spartianus” but to another pseudonym, “Trebellius Pollio.” ⁷⁷ This apparent contradiction is not especially troubling because in distributing the biographies among his six fictitious “authors,” the real author of the Historia Augusta routinely mixed up his attributions.⁷⁸ If Pirro saw a copy of the now-lost biography of Decius, it may well have been attributed in the text to “Aelius Spartianus.” Alternatively, if Pirro’s Decius text was unattributed, he may have assumed that “Spartianus” was the author, because elsewhere “Spartianus” announces that he plans to write biographies of all the emperors and caesars.⁷⁹

At first glance the anecdote Pirro attributes to “Spartianus” makes no sense at all. Built in the late 1st c. B.C.E. by Augustus’ son-in-law, the thermae Agrippae was Rome’s first public bath, one of the best-known buildings in the city.⁸⁰ If Decius had claimed to have built the Baths of Agrippa, it would have earned him only derision. However, we should consider the possibility that the original notice in the Historia Augusta referred not to the thermae Agrippae but to the thermae Philippicae. Since the “Baths of Philip” were unknown, a medieval copyist may have emended Philippicae to the more familiar Agrippae. Or it may have been Pirro himself, a scholar who took great delight in correcting the errors of others, who made the change. If Pirro were convinced that the correct reading was thermae Agrippae, it would have been logical for him to translate a verb such as perficere as Italian ristaurare. After all, in Decius’ time the Baths of Agrippa had been for hundreds of years, but they would certainly have been in need of repair.