Lives of the Stoics: The Art of Living From Zeno to Marcus Aurelius

It cannot be said that the Stoics, like some philosophers, were interested only in their proofs or debates. Posidonius perfectly illustrates the curiosity, the fascination with the beautiful and complex world that surrounds us which defined Stoicism in the ancient world and continues today. You can and should be interested in everything, the Stoics taught, because you can and should learn wisdom from everything. The more you experience, the more you learn, and, paradoxically, the more humbled you are by the endless amounts of knowledge that remain in front of you.

As Posidonius traveled, his reputation grew as the greatest polymath since Aristotle. He measured tides in Spain and conducted ethnographic research on the Celts in Gaul. He was a keen observer and a lover of data—regardless of the discipline—and a diligent recorder of it all. He measured the circumference of the earth, the size and distance of the sun and the moon, created models of both the globe and the known solar system. The only constraint on his brilliance was the crude measuring tools of his age, which often skewed his calculations. Still, his ceaseless travel and unmatched curiosity dramatically increased the understanding of the known universe at that time.

It also got him outside, down in the dirt and out on the water. His classroom was the sky and the stars and the bustling marketplace, as it had been for Zeno, as it is for the child who can be fascinated even by an ordinary patch of grass. Posidonius lived, as Seneca would later write, as if the whole world was a temple of the gods.

Some geniuses are content to live entirely in their own heads. Many philosophies—filled with philosophers who no doubt see themselves as geniuses—subtly encourage this tendency. Epicureanism, for instance, which was resurgent in Posidonius’s time, encouraged its followers to turn away from the world, to ignore politics and the noise around them. Posidonius, thanks to the influence of Stoics like Diogenes and Panaetius, resisted the pull of this bubble and, like a good Stoic, also turned his intellect to politics and governance.

Indeed, his far-flung travels brought him in constant contact with Roman legions, legions that had been trained for Marius by his fellow Stoic and student of Panaetius, Rutilius Rufus. We see evidence from the fragments of his writings that Posidonius studied troop movements, the history of warfare, and the customs of local people, and even gathered intelligence about foreign powers, which he not only provided to generals but later used in his many books. He even wrote a manual on military tactics, a kind of Art of War, that was so detailed that it was considered too advanced for anyone but a general. In addition to becoming a repository of military tactics, he also had deep ethnographic insights gathered from the foreign territories, which generals like Pompey would seek from him for many years.

He was the complete man. An explorer. Strategist. Scientist. Politician. He was, then, a real philosopher.

At some point, though, every traveler must come home, which for Posidonius became Rhodes. Putting his study of politics into practice, he rose in the leadership ranks there to the highest civil position of prytany, presiding over the governing council in Rhodes while building up his philosophical school.

His political duties would bring him to Rome in 86 BC on embassy, but it was likely his curiosity and desire to study human beings that brought him to the deathbed of one of Rome’s worst strongmen, Marius. Marius was elected to his seventh consulship in late 87 BC, and seemed to think that his political power made him immortal. He could not have imagined that Posidonius would be one of the last faces he would ever see.

Delusional, tortured by dark dreams, wearied by a life of endless ambition and the creeping fear that it had all been for naught, Marius received Posidonius, a keen observer, who was repulsed by what he saw. A few days after the meeting, Marius died, convinced until the end that he would once again be leading troops in battle and expanding his conquests. As a Stoic, Posidonius must have noted—as Plutarch would—what a far cry this was from the peaceful passing of a philosopher like Antipater, who had spent his final moments counting the blessings of his voyage through life.

It’s a timeless question: If you actually knew what “success” and “power” looked like—what it did to the people who got it—would you still want it?

Posidonius’s later writings are filled with firsthand observations about the costs of ambition and insatiable appetites. In one of his histories, he writes of a philosopher named Athenion, who had designs on becoming a tyrant in Athens. It must have struck Posidonius how easily people can be corrupted and cut off from virtue, for here was a man with similar training who had abandoned his genius to marry a prostitute and depended on the mob for his own political advancement.