Posidonius
Posidonius "of Apameia" or "of Rhodes" , was a Greek politician, astronomer, astrologer, geographer, historian, mathematician, and teacher native to Apamea, Syria. He was considered the most learned man of his time and, possibly, of the entire Stoic school. After a period learning Stoic philosophy from Panaetius in Athens, he spent many years in travel and scientific researches in Spain, Africa, Italy, Gaul, Liguria, Sicily and on the eastern shores of the Adriatic. He settled as a teacher at Rhodes where his fame attracted numerous scholars. Next to Panaetius he did most, by writings and personal lectures, to spread Stoicism to the Roman world, and he became well known to many leading men, including Pompey and Cicero.
His works are now lost, but they proved a mine of information to later writers. The titles and subjects of more than twenty of them are known. In common with other Stoics of the middle period, he displayed syncretic tendencies, following not just the earlier Stoics, but making use of the works of Plato and Aristotle. A polymath as well as a philosopher, he took genuine interest in natural science, geography, natural history, mathematics and astronomy. He sought to determine the distance and magnitude of the Sun, to calculate the diameter of the Earth and the influence of the Moon on the tides.
Life
Early life and education
Posidonius, nicknamed "the Athlete", was born around 135 BC. He was born into a Greek family in Apamea, a Hellenistic city on the river Orontes in northern Syria. As historian Philip Freeman puts it: "Posidonius was Greek to the core". Posidonius expressed no love for his native city, Apamea, in his writings and he mocked its inhabitants.As a young man he moved to Athens and studied under Panaetius, the leading Stoic philosopher of the age, and the last undisputed head of the Stoic school in Athens. When Panaetius died in 110 BC, Posidonius would have been around 25 years old. Rather than remain in Athens, he instead settled in Rhodes, and gained citizenship. In Rhodes, Posidonius maintained his own school which would become the leading institution of the time.
Travels
Around the 90s BC Posidonius embarked on a series of voyages around the Mediterranean gathering scientific data and observing the customs and people of the places he visited. He traveled in Greece, Hispania, Italy, Sicily, Dalmatia, Gaul, Liguria, North Africa, and on the eastern shores of the Adriatic.In Hispania, on the Atlantic coast at Gades, Posidonius could observe tides much higher than in his native Mediterranean. He wrote that daily tides are related to the Moon's orbit, while tidal heights vary with the cycles of the Moon, and he hypothesized about yearly tidal cycles synchronized with the equinoxes and solstices.
In Gaul, he studied the Celts. He left descriptions of customs such as nailing skulls to doorways as trophies, which he witnessed, and vivid legends told to him by the Celts, such as a story that in the past, men were paid to allow their throats to be slit for public amusement. But he noted that the Celts honored the Druids, whom Posidonius saw as philosophers, and concluded that, even among the barbaric, "pride and passion give way to wisdom, and Ares stands in awe of the Muses." Posidonius wrote a geographic treatise on the lands of the Celts which has since been lost, but which is referred to extensively in the works of Diodorus of Sicily, Strabo, Caesar and Tacitus' Germania.
Political offices
In Rhodes, Posidonius actively took part in political life, and he attained high office when he was appointed as one of the Prytaneis. This was the most important political office in Rhodes, combining presidential and executive functions, of which there were five men holding the office for a six-month period.He was chosen for at least one embassy to Rome in 87/86, during the Marian and Sullan era. Although the purpose of the embassy is unknown, this was at the time of the First Mithridatic War when Roman rule over the Greek cities was being challenged by Mithridates VI of Pontus and the political situation was delicate.
The Stoic school on Rhodes
Under Posidonius, Rhodes eclipsed Athens to become the new centre for Stoic philosophy in the 1st century BC. This process may have already have begun under Panaetius, who was a native of Rhodes, and may have fostered a school there. Ian Kidd remarks that Rhodes "was attractive, not only as an independent city, commercially prosperous, go-ahead and with easy links of movement in all directions, but because it was welcoming to intellectuals, for it already had a strong reputation particularly for scientific research from men like Hipparchus."Although little is known of the organization of his school, it is clear that Posidonius had a steady stream of Greek and Roman students, as demonstrated by the eminent Romans who visited it. Pompey sat in on a lecture in 66 and did so again in 62 on return from campaigning in the East. On this latter occasion the subject of the lecture was "There is no good but moral good". Posidonius was probably in his seventies at this time and was suffering from gout. He illustrated the theme of his lecture by pointing to his painful leg and declaring "It is no good, pain; bothersome you may be, but you will never persuade me that you are an evil."
When Cicero was in his late twenties, he attended a course of Posidonius' lectures, and later invited Posidonius to write a monograph on Cicero's own consulship. In his later writings Cicero repeatedly refers to Posidonius as "my teacher" and "my dear friend". Posidonius died in his eighties in 51 BC; his grandson, Jason of Nysa, succeeded him as head of the school on Rhodes.
Partial scope of writings
Posidonius was celebrated as a polymath throughout the Graeco-Roman world because he came near to mastering all the knowledge of his time, similar to Aristotle and Eratosthenes. He attempted to create a unified system for understanding the human intellect and the universe which would provide an explanation of and a guide for human behavior.Posidonius wrote on physics, astronomy, astrology and divination, seismology, geology and mineralogy, hydrology, botany, ethics, logic, mathematics, history, natural history, anthropology, and tactics. His studies were major investigations into their subjects, although not without errors.
None of his works survives intact. All that have been found are fragments, although the titles and subjects of many of his books are known. Writers such as Strabo and Seneca provide most of the information about his life and works.
Philosophy
For Posidonius, philosophy was the dominant master art and all the individual sciences were subordinate to philosophy, which alone could explain the cosmos. All his works, from scientific to historical, were inseparably philosophical.He accepted the Stoic categorization of philosophy into physics, logic, and ethics. These three categories for him were, in Stoic fashion, inseparable and interdependent parts of an organic, natural whole. He compared them to a living being, with physics the flesh and blood, logic the bones and tendons holding the organism together, and finally ethics—the most important part—corresponding to the soul.
Although a firm Stoic, Posidonius was syncretic like Panaetius and other Stoics of the middle period. He followed not only the earlier Stoics, but made use of the writings of Plato and Aristotle. Posidonius studied Plato's Timaeus, and seems to have written a commentary on it emphasizing its Pythagorean features. As a creative philosopher, Posidonius would however be expected to create innovations within the tradition of the philosophical school to which he belonged. David Sedley remarks:
Ethics
Ethics, Posidonius taught, is about practice not just theory. It involves knowledge of both the human and the divine, and a knowledge of the universe to which human reason is related.It was once the general view that Posidonius departed from the monistic psychology of the earlier Stoics. Chrysippus had written a work called On Passions in which he affirmed that reason and emotion were not separate and distinct faculties, and that destructive passions were instead rational impulses which were out-of-control. According to the testimony of Galen, Posidonius wrote his own On Passions in which he instead adopted Plato's tripartition of the soul which taught that in addition to the rational faculties, the human soul had faculties that were spirited and desiderative. Although Galen's testimony is still accepted by some, more recent scholarship argues that Galen may have exaggerated Posidonius' views for polemical effect, and that Posidonius may have been trying to clarify and expand on Chrysippus rather than oppose him. Other writers who knew the ethical works of Posidonius, including Cicero and Seneca, grouped Chrysippus and Posidonius together and saw no opposition between them.
Physics
The philosophical grand vision of Posidonius was that the universe itself was interconnected as an organic whole, providential and organised in all respects, from the development of the physical world to the behaviour of living creatures. Panaetius had doubted both the reality of divination and the Stoic doctrine of the future conflagration, but Posidonius wrote in favour of these ideas. As a Stoic, Posidonius was an advocate of cosmic "sympathy" —the organic interrelation of all appearances in the world, from the sky to the Earth, as part of a rational design uniting humanity and all things in the universe. He believed valid predictions could be made from signs in nature—whether through astrology or prophetic dreams—as a kind of scientific prediction.Mathematics
Posidonius was one of the first to attempt to prove Euclid's fifth postulate of geometry. He suggested changing the definition of parallel straight lines to an equivalent statement that would allow him to prove the fifth postulate. From there, Euclidean geometry could be restructured, placing the fifth postulate among the theorems instead.In addition to his writings on geometry, Posidonius was credited for creating some mathematical definitions, or for articulating views on technical terms, for example 'theorem' and 'problem'.