## November 5, 2006

### Puzzle #5

#### Posted by John Baez

When was the Roman empire sold, and who bought it?

(Extra credit: how much did it cost?)

Posted at November 5, 2006 9:46 PM UTC

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### Re: Puzzle #5

In Book Two, “The Year of Five Emperors”, of Herodian’s History of the Roman Empire, it is told how in the year 193 (as we count) Pertinax becomes emperor, is murdered by angry soldiers, and the empire is sold to prefect Didius Julianus. I believe that he paid the soldiers of the guard 30,000 sesterces, but am not sure if that was the price in question. Do I get a least partial credit?

Posted by: Jonathan Vos Post on November 6, 2006 12:44 AM | Permalink | Reply to this

### Re: Puzzle #5

Jonathan Vos Post wrotes:

Do I get a least partial credit?

Full credit! And, if we combine your answer with what I know, we should in theory be able to deduce the number of soldiers! At least we would if we knew one more fact…

Q: When was the Roman empire sold, and who bought it?

A: On March 28th, 193 AD, the Roman empire was auctioned off by the Praetorian guards to the wealthy senator Didius Julianus for the price of 6250 drachmas per soldier.

The Praetorian guards had murdered the emperor Pertinax, and after some discussion with the emperor’s father-in-law Sulpicianus, who offered 5000 drachmas each to the officers to be made emperor, they decided to sell Roman empire to the best bidder by public auction. In the words of Edward Gibbon,

This infamous offer, the most insolent excess of military licence, diffused an universal grief, shame, and indignation throughout the city. It reached at length the ears of Didius Julianus, a wealthy senator, who, regardless of the public calamities, was indulging himself in the luxury of the table. His wife and his daughter, his freedmen and his parasites, easily convinced him that he deserved the throne, and earnestly conjured him to embrace so fortunate an opportunity. The vain old man hastened to the Praetorian camp, where Suplicianus was still in treaty with the guards, and began to bid against him from the foot of the rampart.

After outbidding Sulpicianus, Didius Julianus was named emperor, and he received an oath of allegiance from the guards. In Gibbons’ eloquent words:

A magnificent feast was prepared by his order, and he amused himself until a very late hour, with dice, and the performances of Pylades, a celebrated dancer. Yet it was observed that after the crowd of flatterers dispersed, and left him to darkness, solitude, and terrible reflection, he passed a sleepless night; revolving most probably in his mind his own rash folly, the fate of his virtuous predecessor, and the doubtful and dangerous tenure of an empire, which had not been acquired by merit, but purchased by money.

After the armies of Britain, Syria and Pannonia declared against Julian, a civil war began. The Praetorian guards eventually deserted Didius Julianus, and he was condemned and executed by the Roman Senate on June 2nd of the same year.

Source: Edward Gibbon, The Decline and Fall of the Roman Empire, chapter V, volume I, first published in 1776.

Posted by: John Baez on November 6, 2006 4:59 AM | Permalink | Reply to this

### Re: Puzzle #5

What’s the relative value of drachma vs. sestertius? I would have thought that this would help, but evidently I’m not reading it right.

Posted by: Allen Knutson on November 6, 2006 5:14 AM | Permalink | Reply to this

### Re: Puzzle #5

The drachma was Greek, while the sestertius Roman; for their conversion rate in 193 AD we may need to consult with Robert Dickof, who wrote the devastatingly erudite addendum to week229, on Roman coinage and the “quincunx”.

My prose style has just been affected by rereading a bit of Gibbons’ Rise and Fall.

Posted by: John Baez on November 6, 2006 5:29 AM | Permalink | Reply to this

### Re: Puzzle #5

Excellent. That’s how the late Dr. Isaac Asimov came to write “The Foundation” and sequelae. Even after starting college, he couldn’t decide whether to be a Chemist or an Historian. He went with Biochemistry (I think he and I were the first two American Science Fiction authors to do theses in Enzymology) but explicitly wrote “The Foundation” as a morphism of Gibbons to galactic scale. Late in life, he wrote a story undercutting the premise of Psychohistory (in his quantum human statistical sense) due to Chaos.

Posted by: Jonathan Vos Post on November 6, 2006 5:37 AM | Permalink | Reply to this

### Re: Puzzle #5

So, in order to do their psychohistorical calculations, do the members of Asimov’s Foundation use foundational mathematics?

Sorry, it’s been a long day.

Posted by: Blake Stacey on November 8, 2006 10:28 PM | Permalink | Reply to this

### Re: Puzzle #5

As Isaac Asimov’s friend, published in one of his anthologies, who brought him as my guest when I appeared live on The NBC-TV Today Show, I am positive that he would have been delighted by this deep pun. Good link, too. I’ve been wondering how well the Von Neumann Universe and Godel Universe have been reconceived in Category and n-Category Theory approaches.

Posted by: Jonathan Vos Post on November 8, 2006 10:36 PM | Permalink | Reply to this

### Re: Puzzle #5

In 193 Didius Julianus did not buy the empire from the army as a whole, only from the praetorian guard of Rome - thus his eventual undoing by Septimius Severus. (The senate did vote to execute Didius Julianus as you say; I only suggest that the presence of Septimius Severus at the head of his legions may have helped to frame the debate.) The point here is that praetorians in Rome were almost certainly paid with Roman coinage; the drachm was Greek.

Cassius Dio, another ancient historian who covered this period (trans. Earnest Cary, Loeb Classical Library, Harvard University Press, 1927), refers to a bid of 20,000 δραχμων (“drachmon” - which Cary translated as sestertii) per soldier by Didius’ rival. He then goes on to say “Sulpicius would have won the day, being inside and being prefect of the city and also the first to name the figure twenty thousand, had not Didius Julianus raised the bid no longer by a small amount but by five thousand at one time, both shouting it in a loud voice and also indicating the amount with his fingers.”

I think that the final bid was 25,000 sestertii. The bidding was in sestertii because that was the unit of account in Rome (as the dollar is in North America rather than the penny, nickel or fiver). That does not imply that each soldier was handed 25,000 bronze sestertii (~500 kg). Larger sums could be paid with silver denarii (worth four sestertii) or gold aureii (usually worth 25 denarii or 100 sestertii). The soldiers might have received 6250 denarii (~21 kg) or 250 aureii (<1 kg). The last seems most likely. Herodian and Dio were Greeks who wrote in Greek and used the word drachma because that was the Greek unit of account - what their Greek audience would recognise. Many cities continued to mint drachm-based coinages (mostly in the form of a four-drachm silver piece called a tetradrachm) on a variety of weight standards well into the empire. The cistophorus (“basket bearer” from a design that they had borne much earlier) was a very common tetradrachm produced throughout Asia Minor for hundreds of years. Originally, it was worth 3 denarii, but by 193 was worth four denarii. Herodian has translated 6250 denarii into 6250 drachms; his intent was to convey the value. Dio used the word drachm to refer to sestertii; his intent was to convey the story.

Posted by: Peter Dickof on November 7, 2006 3:34 AM | Permalink | Reply to this

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