Why did Marcus Aurelius allow Commodus to succeed him?

This is a first draft.  I’ve not supplied detailed references because I’m writing it off the top of my head just to get it out there.  Please correct any errors.  I’ll check it later and add references, etc.  So apologies for any typos or whatever!

One of the most commonly asked questions on my Facebook group for Stoicism is why Marcus Aurelius, one of the good emperors, would have allowed Commodus, who turned out to be a terrible emperor, to succeed him.  Sometimes people are just puzzled by this.  Sometimes they criticize Marcus for failing in his duty either to bring up a better son or appoint a better heir.  Sometimes they’ve seen the Hollywood movie Gladiator (2000), which focuses on the character of Commodus as a bad emperor, and ask questions about its historical accuracy.  It’s a question that interests me because I run a course about the relationship between Marcus Aurelius’ life and his Stoic philosophy called How to Think Like a Roman Emperor, and I’ve just finished writing a book on the same subject.

Marcus and Commodus in Gladiator

Let me start by briefly recapping what happens in Gladiator because those images seem to influence a lot of these discussions…  In the first act, Commodus (Joaquin Phoenix) is depicted as Caesar, the heir to the Roman empire, with his father, the Emperor Marcus Aurelius (Richard Harris), on the northern frontier, during the Second Marcomannic War.  A frail and elderly Marcus tells Commodus that he has changed his mind about appointing him emperor and that one of his generals, Maximus (Russell Crowe), will serve as an interim ruler managing Rome’s transition back to a republic.

MARCUS: Are you ready to do your duty for Rome?
COMMODUS [with a slight smile on his face]: Yes, father.
MARCUS: You will not be Emperor.
COMMODUS [the smile quickly vanishes leaving in its place painful bewilderment]: Which wiser, older man is to take my place?
MARCUS: My powers will pass to Maximus to hold in trust until the Senate is ready to rule once more. Rome is to be a Republic again.

Commodus then strangles his father, makes himself emperor anyway, and tries to have Maximus murdered, setting up the plot for the rest of the film.

There’s also a Netflix docuseries about Commodus called Roman Empire: Reign of Blood (2016), which approaches the subject from a slightly more historical perspective.  Several academics appear as talking heads, discussing Marcus Aurelius and Commodus, and dramatized sections are interspersed depicting the events of his life.  The experts are fairly reliable but the dramatized segments are a little hit and miss in their depiction, inevitably, as they have to make things exciting for the viewer and where there’s some uncertainty or conflict in the ancient sources they sometimes pick the most sensational story to tell.

Some Key Facts

This is a slightly complicated story.  However, I find it helps to begin just by stating a few important historical facts, which I believe are partly obscured by the portrayal of events in Gladiator, although even people who have never seen that movie are often mistaken on these points.

1. At the time Commodus was appointed heir, Marcus was still ruling alongside his adoptive brother and co-emperor, Lucius Verus, who was nine years younger, and much fitter than the notoriously frail and sickly Marcus, so presumably Lucius was expected to be Marcus’ immediate successor.
2. Marcus and Lucius together appointed Commodus Caesar, official heir to the throne, along with his younger brother, Marcus Annius Verus, on 12th October 166, when Commodus was a child aged five years old.  Presumably at this time the most likely scenario would have been that when Marcus died, Commodus would serve alongside Lucius Verus as his junior co-emperor.
3. Commodus had already been ruling as Emperor for about three years before Marcus died.  Marcus had his son acclaimed Imperator on 27th November 176 AD and later, in the summer of 177 AD, he was granted the title Augustus, making him co-emperor with Marcus.

So whereas Commodus is portrayed as Caesar in the movie Gladiator, waiting to succeed Marcus, who then refuses to let him take the throne, in reality Commodus had already been emperor for about three years before Marcus died.  Incidentally, although there were rumours that Commodus had Marcus assassinated, which Cassius Dio repeats, he also says that when Marcus was dying he took the precaution of having his son taken under armed guard so that he couldn’t be accused of his murder.

[Marcus Aurelius] passed away on the seventeenth of March, not as a result of the disease from which he still suffered, but by the act of his physicians, as I have been plainly told, who wished to do Commodus a favour.  When now he was at the point of death, he commended his son to the protection of the soldiers (for he did not wish his death to appear to be due to Commodus) […] (Cassius Dio)

Marcus was nearly sixty and apparently dying of the plague, so it hardly seems necessary for Commodus to have gone to the trouble of ordering his physicians to assassinate him, although it’s possible.

Hadrian’s Succession Plan

Now let’s get a little deeper into the complexities…  Imperial succession arrangements were often complicated and mysterious.  To understand Commodus we have to go right back to his great-grandfather, by adoption, the emperor Hadrian.  Hadrian was childless.  Toward the end of his life his behaviour was becoming erratic.  He surprised everyone by choosing a man called Lucius Ceionius Commodus as his successor.  Hadrian granted him the  imperial title Caesar, starting a tradition that the heir to the throne would take that title in advance.  However, the man died suddenly about a year later, forcing Hadrian to come up with another candidate.

He then adopted a man called Aurelius Antoninus and appointed him Caesar on condition that Antoninus would in turn adopt a young boy called Marcus Annius Verus and make him his own successor.  The boy Marcus took Antoninus’ family name and became forever known as Marcus Aurelius.  So there was a plan that stretched decades into the future.  However, these arrangements could easily be overturned by events.  The man Hadrian had originally appointed Caesar had a young son, also called Lucius.  The Senate were terrified of the possibility of civil war caused by rival factions fighting over claims to the throne.  When Hadrian died he was hated by the Senate for spying on and executing his enemies at Rome.  He’d also left them with the problem of what to do about the boy Lucius.

Marcus and Lucius as Co-Emperors

When the Emperor Antoninus died, Marcus Aurelius was acclaimed emperor but he insisted that the Senate recognize Lucius as his co-emperor.  Lucius then took Marcus’ family name and became the Emperor Lucius Verus.  Lucius was also betrothed to Marcus’ young daughter, Lucilla, making him Marcus’ son-in-law as well as his adoptive brother.  (I know, it’s confusing but bear with me…)  This was the first time that Rome had been ruled by two emperors jointly.  It was probably considered necessary to unite the empire and prevent instability caused by the mess Hadrian had left by creating two rival dynasties with a claim on the throne.

The histories make it clear that although on paper they were  (virtually) equals, Marcus was effectively the senior party and Lucius obeyed him like a provincial governor or a lieutenant in the army.   I won’t go too much into Lucius’ character except to say he was quite the opposite of Marcus and whereas Marcus was a workaholic who spent his youth tirelessly studying and gaining experience of Roman law and government, Lucius was very idle and clearly came nowhere near Marcus’ level of competence and experience as a ruler.  The one thing Marcus lacked was any military experience.  As far as we know Lucius didn’t have any either but he was young, handsome, obsessed with sports, and probably quite popular, so it seems his role was envisaged as having more to do with the military.  When the two emperors were acclaimed, indeed, it was Lucius who was sent to deliver a speech to the soldiers, and not long after, when the Parthian War broke out, Marcus sent Lucius to Syria to oversee the campaign.

We’ve no direct confirmation of this but it stands to reason that at this point in time it would have been assumed that Lucius would outlive Marcus and effectively become his successor.  Lucius was nine years younger than Marcus and much fitter and healthier than him.  He was also married to Marcus’ daughter, and it was said Marcus treated him more like a son than a brother.  He may also have been a bad emperor but it seems that Marcus felt it was necessary, for some reason, to appoint him.  Presumably because it was feared that a rival dynasty would split the empire, which in turn would leave it vulnerable to invasion, as we’ll see.

Lucius didn’t really distinguish himself during the Parthian War.  He reputedly spent his time partying far away from the action and let his generals do all the work for him.  One in particular, Avidius Cassius, became a rising star, and we’ll be returning to his part in the story later.  However, Lucius returned to Rome and celebrated his victory.  Unfortunately, the Roman legions returning to their garrisons across Europe brought back a disease, probably a strain of smallpox, which became known as the Antonine Plague.  This pestilence ravaged the empire throughout the rest of Marcus’ reign and well into the reign of Commodus.  We’re told bodies were carried out of Rome by the cartload.  It’s been estimated that five million people across the empire may have died as a result of this plague.  The Antonine Plague is an important character in this story because the histories tell us that by taking the lives of so many people it disrupted society in many ways.  Those to whom family fortunes were bequeathed died prematurely.  Experienced senators, military officers, and government officials died prematurely and had to be replaced – there was a high turnover of staff in important positions.  We can see this affected the imperial succession also.

The Marcomannic Wars

Shortly after Lucius returned, a huge coalition army of barbarian tribes from the north, led by King Ballomar of the Marcomanni, invaded the northern provinces of the Roman Empire.  They proceeded across the Alps, Rome’s natural defensive barrier, and rampaged through Italy, finally besieging the Italian city of Aquileia.  This time both Marcus and Lucius took command of the military response and left Rome together to drive the barbarian horde out of Italy and liberate the northern province of Pannonia.  War in the north would occupy Marcus for most of the rest of his reign and it would also cost the lives of many Romans, including men in senior positions.  The city of Rome itself was thrown into total panic by the news that a barbarian army had penetrated Italy, because they feared Rome would be sacked.

Ballomar had seized the opportunity when Rome was weak.  Beleaguered troops were still on their way back to their garrisons in the north from the Parthian War far to the east.  The legions had also been devastated by the plague, which thrived in the conditions found in army camps.  It was at this time that Marcus and Lucius agreed to appoint Marcus’ two sons, Commodus and Marcus Annius Verus, as two Caesars.  This was undoubtedly done in response to the panic at Rome.   Although his own succession had been planned by Hadrian far in advance, Marcus himself wasn’t appointed Caesar by Antoninus until he was eighteen.  It was clearly assumed that both Marcus and Lucius might die suddenly and that it was better to have a successor in place than leave Rome in chaos.  The death rate among children due to the plague would have been particularly high.  That may be one reason why two boys were appointed Caesar but it’s also likely that Marcus planned for the brothers to rule jointly one day, as he and Lucius had done.

People often comment online that the Roman emperors typically adopted their successors and Marcus should have done likewise.  The precedent for this was set when Julius Caesar adopted Octavian who went on to become Augustus, the first Roman emperor.  However, the Roman emperors who adopted heirs normally did so because they had no suitable natural heirs of their own.  For example, Hadrian adopted Antoninus and Antoninus adopted Marcus because they had no sons available to succeed them.  The Roman people actually believed very strongly in natural succession, just like most barbarian peoples did.  An emperor who had a natural heir, like Marcus, and chose to bypass him to adopt an heir, would risk creating a rival dynasty and dividing the empire.  As rivals to the throne were often murdered, adopting a successor would also mean placing his own son’s life in very serious jeopardy.  (On the other hand, as we’ll see, Marcus possibly did consider adopting an interim successor, Pompeianus, who would perhaps have become emperor if Marcus died while Commodus was still a boy, subsequently appointing Commodus his co-emperor, to rule jointly, when he reached a suitable age.)

Roman emperors were habitually family members, and even the adoptions came from a network of close kin; Nerva’s adoption of Trajan was the only known case where family connections did not play a part.  The reasons for keeping the throne ‘in the family’ were partly financial. Since imperial wealth subdivided into the private property of the emperor (fiscus) and the funds in the public treasury (aerarium), and thus this wealth was in turn at least partly linked to the imperial family rather than the ‘job’ of emperor, it was extremely hard for a reigning emperor to exclude a son from the succession without at the same time disinheriting him.  Finally, there were prudential reasons. Meritocracy was all very well, but a meritocratic appointment to the purple would risk almost certain rebellion from the excluded kin of the late emperor. To appoint an emperor on mere talent and ability, then, was to hand him a poisoned chalice. When an emperor finally did exclude his own son (in 306), the result was eighteen years of civil war.  Septimius Severus was being ruthlessly pragmatic in his recommendation. Once Commodus survived infancy, Marcus was faced with a stark choice: he either had to make him his heir or kill him. (McLynn, Marcus Aurelius)

The fact that Marcus’ two sons were appointed Caesar did perhaps create a slight anomaly because the most likely scenario would be that Lucius would have outlived Marcus, as we’ve seen.  There would be two Caesars but only one position open, in that case, for a co-emperor.  So presumably it was envisaged that Commodus would serve as junior co-emperor to Lucius Verus and later, after the death of Lucius, Marcus Annius Verus would join his brother and rule alongside him.  Also, Lucius was childless but if he’d had a son surely it would have created another conflict over succession.  (Rome would have potentially been ruled by an emperor who had a natural heir but had already appointed two sons of his deceased brother as his heirs.)  In any case, I would suggest that the Senate urged Marcus and Lucius to appoint these children Caesars before leaving for war because they felt it was necessary for the stability of the empire.

Death of Lucius and Marcus Annius Verus

Shortly after these wars began on the northern front, two deaths shook the empire and upset these plans.  The young Caesar Marcus Annius Verus died during an operation on a tumour.  Marcus lost about seven children altogether, including several sons.  He was getting old now and Commodus, still a child, was his only surviving son.  Shortly after this, the emperor Lucius Verus suddenly dropped dead, possibly another victim of the plague.  There were, as always, rumours that Marcus had him assassinated but most scholars dismiss this as typical court gossip.  Nevertheless, there was a faction on the Senate who opposed Marcus’ ongoing campaign in the north and they possibly propagated these and other rumours against him.

Around this time, Marcus also lost his main Stoic mentor, Junius Rusticus, who was back at Rome serving as urban prefect.  So he must have felt increasingly isolated.  I believe there are signs in The Meditations and in the histories that Marcus was greatly affected by the loss of his children and struggled to cope emotionally by leaning more heavily on his Stoic training.  (Did he perhaps begin writing The Meditations partly as a way of coping with the loss of his tutors and family members?)  I think the whole empire was worried that Commodus wouldn’t survive, during the plague when many children died.  And I think we can see hints that Marcus was affected by this climate and also concerned about the possible loss of his only surviving son, especially now that Lucius was gone.  All eyes were  suddenly on Commodus, though still a child.

The children of Roman nobles were usually raised by nurses who were slaves and possibly their mothers took some part in their care but often they had little contact with their fathers until they became older.  On the other hand, Marcus’ private letters to Fronto reveal him to be an incredibly affectionate man and a loving parent.  He describes his children as his little chicks in a nest.  (These displays of familial affection seem perhaps a little out of character for a Roman of this period.)  Nevertheless, for most of Commodus’ youth Marcus was extremely busy.   With no military experience whatsoever, after the death of Lucius Verus, Marcus was suddenly and unexpectedly left in command of the largest army ever massed on a northern frontier, numbering an estimated 140,000 men, including legions, auxiliary units, naval units on the Danube, etc.  Marcus was mostly stationed at the front line, in Pannonia (modern Austria), several weeks’ travel away from Rome.  It seems his family sometimes visited him but generally we have to assume he was just far to busy fighting a massive campaign and running the empire in a time of great turmoil, far away from Rome, to have had much time to participate in his son’s upbringing.  Nevertheless, we’re told Marcus took great care to provide the best possible tutors for his son, presumably men of good character and wisdom.

Pertinax and Pompeianus

The plague and war took the lives of many men whose positions had to be filled, so it created the opportunity to promote new men.  Marcus caused some controversy by promoting individuals of humble stock, based on merit.  One of them, Pertinax, was the son of a freedman who rose to become one of Marcus’ two right-hand men during the Marcomannic Wars.  Later, he would succeed Commodus and,this son of a former slave would, albeit briefly, become emperor.  The other was Tiberius Claudius Pompeianus, a Syrian of humble origins who had distinguished himself during the Parthian War.  He was close friends with Pertinax and rose to become Marcus’ most senior general on the northern frontier.

Marcus betrothed Pompeianus to his daughter, Lucilla, the widow of Lucius Verus.  She was one of the most powerful women in Rome, being titled Augusta, empress, from her marriage to Lucius, and also a daughter of the Emperor Marcus Aurelius.  By marrying her, Pompeianus was brought into Marcus’ dynasty.  It was rumoured that Marcus asked Pompeianus to become Caesar, presumably as an interim ruler while Commodus matured and gained experience.  However, for some mysterious reason he refused.  Indeed, it’s said Pompeianus was invited to become emperor three times altogether and refused each time.  (Marcus invited him to become Caesar, Pertinax asked him to accede to the throne after Commodus was assassinated and Julianus who succeeded Pertinax asked him to become joint emperor with him.)

Pompeianus was probably almost as powerful as Avidius Cassius, another Syrian general.  However, Cassius was of extremely noble birth and “born to rule” so I would suspect he possibly resented the fact that his rival was a countryman from the lower ranks of society.  We can’t know for sure but I wonder whether Pompeianus refused the invitation to become Marcus’ successor because he was concerned it would incite Cassius to declare civil war.  We’re told Pompeianus later lost his eyesight, which was a common consequence of the plague, due to the pustules spreading onto the eyes.  It may be that in later life he felt he wasn’t physically up to the task of ruling and it’s a sign of the esteem in which he was held, perhaps, that he was twice invited to rule despite being almost blind.  The Aurelian Column which depicts Marcus’ campaign on the northern frontier shows him with Pompeianus by his side.  Incidentally, Russell Crowe’s character the general named Maximus in Gladiator appears to be loosely based on Pompeianus.

The Civil War of Avidius Cassius

Then something else happened that sheds considerable light on the status of Commodus.  Marcus was notoriously sickly.  During the winter of 174/175 AD he seems to have become extremely ill and rumours of his death spread across the empire like wildfire.  This led to Avidius Cassius being acclaimed emperor by the Egyptian legion, far away in the east.  Marcus survived, however, and this led to a civil war.  Cassius was a notoriously strict and brutal military commander.  He’d climbed rapidly to power following the Parthian War and after quelling a huge uprising in Egypt, he was now effectively governor-general over the whole of the eastern empire.   It’s said that after the death of Lucius Verus, six years earlier, he began plotting against Marcus.  By this point he was probably the second most powerful man in the empire next to Marcus himself.  The prefect of Egypt gave him his support as did most of the eastern provinces, and a number of senators.

So we can probably assume that for many years, Marcus was aware that Cassius presented a potential threat and he was cautious about a situation like this arising.  Although Commodus turned out to be a bad emperor, his character at this point was probably unknown to Marcus.  However, Cassius was known to be a brutal man and Marcus and the Senate perhaps feared the possibility that he would claim the throne and become a tyrannical ruler.  Although we often have ambiguous historical information about the motives of these individuals, we can once again see very clearly what actions Marcus took in response to this crisis.

He immediately had Commodus brought from Rome to the military camp in Pannonia.  Commodus happened to be fifteen years old now so Marcus had him take the toga virilis, signifying that he had become an adult Roman citizen.  It seems clear that Marcus wanted to protect Commodus from danger, to build support for him among the northern legions, and to put him in a position to assume power so that there was less uncertainty over the succession.  From this point on, Commodus remained in his father’s company.  So we could argue that Marcus now had time to mentor his son and study his character.  However, it’s far too late now for Marcus to change course.  He couldn’t strip Commodus of the title Caesar, granted to him ten years earlier.  If he wanted to stop Commodus becoming his successor his only real option would be to have him assassinated, which would be against his Stoic Ethics.  Even if he’d stripped Commodus of the title Caesar, he would have created a situation where he remained in the wings as a potential rival to any successor, around whom opposing factions could rally, splitting the empire in another civil war.

Marcus and Commodus as Co-Emperors

Marcus successfully put down the civil war and Cassius was beheaded by his own officers.  As noted above, Commodus was then rapidly promoted to the rank of co-emperor.  Some of the histories suggest that Marcus now began to realize that Commodus was going to be a bad emperor.  However, we’re also told that he wasn’t so much a bad person as a weak or gullible one.  He was easily swayed by hangers-on.

This man [Commodus] was not naturally wicked, but, on the contrary, as guileless as any man that ever lived. His great simplicity, however, together with his cowardice, made him the slave of his companions, and it was through them that he at first, out of ignorance, missed the better life and then was led on into lustful and cruel habits, which soon became second nature.  And this, I think, Marcus clearly perceived beforehand. Commodus was nineteen years old when his father died, leaving him many guardians, among whom were numbered the best men of the senate. But their suggestions and counsels Commodus rejected, and after making a truce with the barbarians he rushed to Rome; for he hated all exertion and craved the comfortable life of the city. (Cassius Dio)

In particular, Marcus asked his son-in-law and most trusted general, Pompeianus, to take responsibility for Commodus after his death and keep him out of trouble.  After Marcus died, with Commodus now as sole emperor, it’s said that he immediately sought to abandon the northern campaign by paying huge bribes to the barbarian kings, so that he could return to Rome.  We’re told Pompeianus was the only one brave enough to confront the new emperor and challenge his behaviour, arguing that he must remain with the army and finish the campaign.

So there was allegedly a sort of tug-of-war between Pompeianus and Commodus’ friends.  After a few weeks, his friends won and Commodus abandoned the legions to return to Rome.  There wasn’t much that Pompeianus could do to stop him.  In one fell swoop, he’d lost all credibility with the army.  An emperor normally requires the support of the legions or the Senate or the people of Rome.  I think Commodus was now forced to become a populist in order to secure his position.  Without the support of the legions or the Senate he turned himself into a sort of celebrity, fighting in the arena, throwing extravagant spectacles for the people and building a mythology around himself.  He even had statues erected portraying himself as the Greek hero (and deity) Hercules, bearing his distinctive club and lion-skin headdress.

Was Marcus to Blame?

I’ll let others decide to what extent Marcus was to “blame” for Commodus.  To me it seems that Marcus and the Senate were struggling to prevent civil war from dividing the empire because they knew that in its weakened state Rome would potentially be overrun by barbarian invaders if rival factions started fighting over the throne.  I think they also planned for joint rule as a safety measure against a bad or tyrannical emperor taking control of Rome but the Marcomannic Wars and the Antonine Plague created turmoil that interfered with these plans.  I also think Marcus tried to surround Commodus with advisors and to put him in the care of Pompeianus as a safety measure but that was negated when Commodus simply fled from the front leaving Pompeianus and others behind, and surrounding himself with individuals at Rome who further corrupted him.  I think he found himself in a situation where he felt it was necessary to become a celebrity rather than a genuine ruler, something Marcus would have warned him against, and that inevitably led him further and further astray.

The Stoics would say that we can’t hold parents responsible for their children.  Even Socrates had wayward sons and students.  You can lead a horse to water but you can’t make it drink.  One of the very early philosophers admired by the Stoics was Stilpo, of the Megarian School, a teacher of Zeno of Citium.  He had a notoriously dissolute daughter, apparently.  People used to hold that against him but Stilpo replied, I think with some justification, “Her behaviour can no more brings dishonour upon me than mine can bring honour upon her.”  I think it’s worth contemplating how that saying might relate to Marcus and Commodus.