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Who Is Posidonius? The Most Academic Stoic


Introduction & Biography

Posidonius was born in the Greek city of Apamea in 135 B.C.E., located in what is now Syria. After he completed his early education in Apamea, he moved to Athens to pursue philosophical study at the Stoic school under Panaetius. Similar to his teacher, Posidonius found himself in disagreement with many of the foundational principles of Stoicism. He often found himself in debates with fellow scholars, siding frequently with Panaetius who was working to usher in the new era of Middle Stoicism.

Unlike with Panaetius, however, reforming Stoicism did not prove satisfying. Posidonius was unable to reconcile his issues with the Stoic tenets and eventually left the school entirely. His departure was also motivated by his desire to explore fields such as geography and astronomy with the same rigorous attention to detail that the Stoic school afforded philosophy. Moving forward, he began to study both Plato and Aristotle in depth, rejecting the rigidity of his educational background.

Following his departure from the Stoic school around 95 B.C.E., Posidonius moved to Rhodes. While the region was famous for its scientific advancements, Posidonius found himself immersed in its political realm. He eventually became a Prytaneis of Rhodes, serving as its primary leader for half a year (the maximum term). In addition, he served as an ambassador to Rome for the region.

It is particularly interesting to note that Posidonius, while straying from Stoicism, was following in the footsteps of his predecessor, Panaetius. Panaetius was born in Rhodes and frequently visited Rome, spreading Stoicism throughout the region. It is unclear if Posidonius consciously decided to imitate his teacher, but it is clear that the teachings of Panaetius emphasized the importance of interacting with international counterparts. 

Similar to Panaetius, Posidonius came to favor Rome as a philosophical and political hotspot. He developed strong relationships with the upper class in Rome, benefiting his own political endeavors as well as his scientific work. These connections provided him with opportunities to travel throughout the known world, expanding his own knowledge. Specifically, Posidonius had the opportunity to travel through the majority of Mediterranean, including North Africa.

Posidonius’s travels inspired many of his great works of writing. Specifically, he had the chance to absorb Celtic practices in Gaul. He came to interpret Celtic practices concerning Druids to be philosophical in nature. He wrote extensively on the region and his treatise on the Celts is frequently referenced in other works. 

Through his political and philosophical endeavors, Posidonius developed a reputation throughout both Greece and Rome. Overtime, students began flocking to Rhodes to study under him. He became viewed as a philosophical authority, effectively serving as Panaetius’s successor despite being located away from the Stoic school in Athens. Following his death in 51 B.C.E., his children maintained his school in Rhodes. 

Today, we understand Posidonius to be one of the greatest polymaths of his time. In other words, he mastered a wide array of subjects, contributing greatly to each. He is known for his work as a philosopher primarily, but excelled in astronomy, geography, mathematics, war practices, history, and politics. 

Notable Works & Suggested Readings

While Posidonius was considered a polymath and excelled in a wide variety of fields, his work in philosophy remains the most influential. In fact, he even believed that all sciences should defer to philosophy, as nothing else could explain the universe as adequately. As a result, many of his works outside of the field take on a philosophical tone.  

Well versed in the Stoic tradition, Posidonius agreed with his predecessors that philosophy was divided into physics, logic, and ethics. His work, however, begins to depart from that of earlier Stoics when we get beyond the basics. Like his immediate predecessor Panaetius, he took an eclectic approach to philosophy. He introduced Platonic and Aristotelian ideas to Stoicism, effectively eliminating many of the discrepancies among the schools of thought. 

He stands out from Panaetius, however, in that he was the first Stoic to suggest that Plato’s conception of the human soul was correct. This meant that passions and desires, rather than false perceptions to be overcome, were an integral part of human identity that must be reasoned with.

While Posidonius’s works have been lost, quotes and citations remain in the works of Cicero, Livy, Plutarch, Strabo, Cleomedes, and Seneca the Younger, among others. He was often praised for his writing style, which was described as extremely stylistic and verging on poetic. Using these sources, we have been able to piece together some of what Posidonius may have written.

It is important, however, to contextualize the work of Posidonius. While he contributed to many fields, his work was often not particularly controversial or original. Instead, he possessed a broad, nuanced understanding of subject material and was able to draw connections between seemingly distant fields of study. Today, we recognize his unified worldview as a major contribution to the field of philosophy, as it was one of the most holistic attempts of his time to explain human behavior and life as a whole.

To learn more about his work among the Celtic Druids, we recommend The Philosopher and the Druids: Journey Among the Ancient Celts by Phillip Freeman. This book serves as a great, simple introduction to the eclectic nature that makes Posidonius so interesting. Afterwards, Posidonius: Volume 3, The Translation of the Fragments pieces together the limited text we have from Posidonius, offering direct access to his genius.

3 Lessons & Exercises 

1) Beware Materialism 

Money and material possessions are not evil to possess. However, they are dangerous. Both envy and greed can encourage us to act poorly in the pursuit of material gain. When material goods become the center of your life, it becomes easy to neglect those around you. Take time to reassess and consider what is motivating your life. What drives you? 


Riches are the cause of evil, not because, of themselves, they do any evil, but because they goad men on to evil.

2) You Are the Company You Keep

The people we surround ourselves with naturally determine the types of conversations we have. Your perspective on the world is dependent on the social circles you choose to craft. It is important to surround yourself with people whose values align with yours and who are equally committed to doing the right thing. Your life will be far more virtuous and impactful surrounded by the right people. 



A single day among the learned lasts longer than the longest life of the ignorant.

3) Do Not Accept Your Lot in Life

In life, it can be easy to play the blame game. How many times have you heard someone say they would make a change if only they had the means to do so? That is no longer an excuse. When you are faced with a challenge, be innovative and refuse to accept your circumstances. Life is not about the hand we’re dealt, but rather how we play it.



There are never any occasions when you need think yourself safe because you wield the weapons of Fortune; fight with your own! Fortune does not furnish arms against herself; hence men equipped against their foes are unarmed against Fortune herself. 


Notable Quotes

Things which bestow upon the soul no greatness or confidence or freedom from care are not goods. But riches and health and similar conditions do none of these things; therefore, riches and health are not goods. Things which bestow upon the soul no greatness or confidence or freedom from care, but on the other hand create in it arrogance, vanity, and insolence, are evils. But things which are the gift of Fortune drives us into these evil ways. Therefore, these things are not goods. 

When men were scattered over the earth, protected by eaves or by the dug-out shelter of a cliff or by the trunk of a hollow tree, it was philosophy that taught them to build houses. 


P.S. The bestselling authors of The Daily Stoic, Ryan Holiday and Stephen Hanselman, have teamed up again in their new book Lives of the Stoics: The Art of Living From Zeno To Marcus. Along with presenting the fascinating lives of all the well-known and not so well-known Stoics, Lives of the Stoics distills timeless and immediately applicable lessons about happiness, success, resilience, and virtue. The book is available for pre-order and is set to release on September 29!


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