Posidonius

Greek philosopher

• Born: c. 135 b.c.e.
• Birthplace: Apamea ad Orontem, Syria
• Died: c. 51 b.c.e.
• Place of death: Unknown, possibly Rhodes (now in Greece)

Though virtually none of his writings survives, it is clear that Posidonius was one of the most influential thinkers of the ancient world. He made important contributions in the fields of philosophy, history, astronomy, mathematics, natural history, and geography.

Early Life

Posidonius (pohs-ih-DOH-nih-uhs) was born in Syria around 135 b.c.e. Some ancient writers refer to him as “The Apamean,” from his birthplace in Syria, which, at that time, was part of the Roman Republic. This vast nation had greatly facilitated the international exchange of knowledge. The dominant philosophy that emerged was Stoicism, named for the Stoa Poecile (the “painted porch”) of the building in Athens where the originators of the doctrine taught. The earliest expression of Stoic philosophy comes from Zeno of Citium (c. 335-261) in Cyprus and Cleanthes of Assos (c. 331-c. 232) in Asia Minor; they were of the Early Stoa, the first period of this doctrine, which lasted from 300 b.c.e. to the beginning of the second century b.c.e. The thinkers of the Middle Stoa introduced this philosophy to Roman culture during the second and first centuries b.c.e. Panaetius of Rhodes (185-109) and his prize student, Posidonius, were the most important figures of the Middle Stoa. Though Stoicism was to remain the dominant philosophy until the second century c.e., Posidonius was the last of the Greek Stoic philosophers.

Posidonius left his home country early in his life and traveled to Athens, where he studied philosophy under Panaetius. After his teacher died in 109, Posidonius traveled for several years throughout North Africa and the western Mediterranean region, including Spain, Italy, and Sicily. During these travels he conducted extensive scientific research. He returned to Greece and settled in Rhodes, the largest island in the Dodecanese group, off the southwest coast of Asia Minor. In Rhodes, he was appointed head of the academy that he would later make the center of Stoic philosophy. Posidonius also became involved in local politics and influenced the course of legislation on more than one occasion. In 87 the Rhodians sent him as an envoy to Rome with the charge of appeasing Gaius Marius. The result of this visit was that Posidonius developed an extreme dislike for Marius and later heavily criticized him in his historical writings.

The Stoic philosophy that Posidonius studied at Athens and taught at Rhodes consisted of three domains of concern: logic, physics, and ethics. Stoic logic included the study of grammar but emphasized the formal nature of reasoning, that is, relations between words, not between words and what they stand for. The relations in rational discourse (as studied by logic) were regarded as reflecting the processes of the cosmos (as studied by physics).

The dominant theme of Stoic physical theory was that the universe is an intelligent living being. The physical theory of the Stoics was equivalent to their theology, for the rational totality was equated with God, Zeus, the logos, or the ordering principles of the universe (all these terms being synonymous within their philosophy). In the physical theory of the Stoics, matter is inert or passive and is acted on by God, the rational active cause. All gradations of being in the universe were regarded as having been formed by this action. According to this philosophy, the action of the rational cause on the matter is cyclical. Throughout the aeons, each cycle begins with the pure active cause organizing the four fundamental elements and ends with a universal conflagration in which all created matter is consumed and the totality reverts to its purified state. Stoic ethical doctrines were perhaps the most famous element of their philosophy and were connected to their cosmological conceptions.

The basic precept of the Stoic ethical system was to live according to the order of the universe. The ultimate goal of ethical action was to achieve self-sufficiency, the only guarantee of happiness. Happiness was regarded as possible only through that which was entirely within the individual’s control, and this state was to be achieved through the practice of the virtues. The most important of the virtues were wisdom, courage, justice, and self-control. The Stoics emphasized two ways of acquiring the virtues: the imitation of exemplary lives and the study of ethics and physics.

It was in the context of these broad doctrines that Posidonius developed his conceptions of humankind and the universe. Though only a few fragments of Posidonius’s writings have survived, he is mentioned by more than sixty ancient writers, and it is through their comments that scholars have been able to reconstruct his philosophy. He is mentioned primarily in the works of Cicero, Strabo, Seneca, and Galen.

Posidonius differed from the Stoic tradition in which he was educated in his concern with empirically oriented scientific investigations. He did, however, adhere to the Stoic division of philosophy into the branches of logic (or dialectics), ethics, and physics. His teacher, Panaetius, admired Plato, and it was with the development of Posidonius’s philosophy that the influence of Plato on Stoicism truly began. Posidonius also emphasized his agreement with the doctrines of Pythagoras, and, in general, he argued for the reconciliation of all opposing philosophies.

Life’s Work

While developing his own version of Stoic philosophy at his academy in Rhodes, Posidonius became quite famous. In 78, the famous Roman orator Cicero attended his school. In fact, Cicero requested of Posidonius that he edit his account (in Greek) of the conspiracy of Catiline. Posidonius declined the request.

Posidonius’s most famous visitor was the Roman general Pompey the Great, who visited Posidonius’s school on two different occasions in order to attend lectures: in 72, when Pompey returned from the eastern part of the Empire after action in the Mithradatic War, and again five years later, after a victorious campaign against pirates in the Mediterranean Sea. As a gesture of respect for the great philosopher, Pompey ordered his officers to lower their fasces (bundles of rods with axes in them, which were used as scepters by Roman leaders) at the door of Posidonius’s school. Posidonius greatly admired Pompey and added an appendix to his Histories (now lost), which was devoted exclusively to Pompey’s campaigns in the East.

Posidonius’s history of the world began with the year 146 b.c.e. (the point at which the famous history of Polybius ended) and continued up to the dictatorship of Lucius Cornelius Sulla around 88 b.c.e. Virtually none of this work has survived, but its influence was tremendous, both at the theoretical level (that is, in the conception of history) and in terms of the sheer mass of factual information that the work contained. All the following historians were influenced by it: Sallust, Julius Caesar, Tacitus, Plutarch, Timagenes, Pompeius Trogus, and Diodorus Siculus.

Posidonius’s Histories was noteworthy for including the histories of the Eastern and Western peoples with whom the Romans had come into contact, such as the Germans and the Gauls. His study of primitive cultures led him to hypothesize that these cultures represented the original state of the more advanced cultures. The work was written from a standpoint that favored the nobility and opposed the Gracchi and the equestrian party. It was also opposed to the independent Greeks, who were supported by Mithradates. In short, the work was strongly pro-Roman, and in it Posidonius attempted to show that Roman imperialism embodied the commonwealth of all humankind and ultimately reflected the commonwealth of God. To this latter commonwealth only those statesmen and philosophers who had lived worthy lives were to be admitted after their stay on earth. In addition, Posidonius argued that lesser civilizations should accept and even welcome Roman domination for the sake of their own self-betterment. This theory had a tremendous influence on Cicero and provided the foundations for the eventual development of the doctrine of natural law.

Posidonius’s conception of the history of the human race was intimately linked to his conceptions of ethics. Politics and ethics were fused within his system, as political virtue consisted in attempting to bring back the natural condition of humanity. In this condition, the philosopher-statesman apprehends the world of God (from which morality is derived) and conveys this vision to the rest of humanity living solely in the material world. Morality and religion were fused in Posidonius’s view, as any moral or political duty was also a religious duty. In a work titled On Duty, Posidonius argued that by adhering to duty, the philosopher-statesman gained knowledge of the spiritual world and freedom and was prepared for the superior forms of existence after death. The highest state to be achieved by a person in this life was regarded by Posidonius as contemplation of the truth and order of the universe (without distraction by the promptings of the irrational part of the soul). Posidonius parted with Stoic orthodoxy on the connection between virtue and happiness, however, and argued that the former was not a sufficient condition for the latter and that external bodily goods were also needed to achieve happiness.

Posidonius also made modifications of Stoic psychological doctrines. The most significant of these was his reaffirmation, in On the Soul, of the division of the soul into rational and irrational parts (the latter being the source of the emotions and appetites). Stoic tradition held to the essential unity of the soul. Posidonius claimed, in On Emotion, that the emotions of the irrational part of the soul have two distinct origins: the body, and judgments of good and evil. He took as evidence for this view the fact that animals, which are irrational creatures, experience emotion. This doctrine also parted from the standard Stoic conception of emotion as based solely on false judgments about good and evil. In this theory, Posidonius drew a connection between the union of the soul and the body and the external influences on that union. He argued that some conditions of the human being are predominantly bodily, whereas others are predominantly spiritual or mental. Some influences pass from the body to the soul, and others pass from the soul to the body. He based a system of character on the idea that permanent modifications of character can be caused by certain bodily organizations.

More fundamental aspects of Posidonius’s psychology are contained in his metaphysical system, in which he followed the standard Stoic conception of two fundamental principles governing the universe: the passive principle (matter) and the active principle (God). God, for Posidonius, did not create the human soul, though the soul was believed to be composed of the same stuff out of which the heavenly bodies are composed. As a result, on the death of the body the soul “escapes” and returns to the heavens. In addition, for Posidonius, God was not the creator of matter, and matter was endowed with its own form and quality. The divine principle merely shaped and modeled this matter (that is, God does not endow matter with form). As part of this cosmology, Posidonius posited, in On Heroes and Daemones, the existence of beings that were intermediary between God and human. These beings were regarded as immortal and were revealed to mortals in visions, divinations, and oracles. Posidonius also regarded the gap between reason and matter as bridged by mathematical forms. Of all the Stoics, only Posidonius was a realist with regard to mathematical entities. In On the Void, he argued that the vacuum beyond the universe was not infinite (a standard Stoic conception) but only large enough to allow for the periodic dissolution of the universe. He also argued that the end of the universe would occur not by fire but by this dissolution.

Among the scientific achievements of Posidonius that were related to his metaphysics was his construction of a model of the celestial system. This planetarium allowed the apparent motions of the sun, moon, and planets around the earth to be exhibited. An important inference he made concerning astronomy, in a work titled On the Sun, was that the sun is larger than the earth because the shadow cast by the earth is conical. He rejected the heliocentric conception of the solar system in favor of a geocentric conception. He also succeeded in calculating the distance between the earth and the sun at 502 million stadia (one stadium equals approximately 600 feet, or 183 meters). The diameter of the sun he calculated at 4 million stadia, and the circumference of the earth at 180,000 stadia, figures that were generally accepted by thinkers in his day. Posidonius also considered the moon to be larger than the earth and to be composed of matter that is transparent. Because of the moon’s size, light does not pass through it during eclipses. In another work on astronomy, On Astronomical Phenomena, Posidonius argued that the Milky Way is composed of igneous material and is intended to warm those parts of the universe that the sun cannot warm. This view was also widely accepted by other thinkers. He had collected considerable geographical data on his various travels, and in On the Ocean he charted the currents of the ocean and pointed out the connection between the tides and the moon. In about 51 b.c.e., Posidonius left Rhodes on another trip to Rome, where he died soon after his arrival. On his death, the school in Rhodes was taken over by his grandson Jason.

Significance

Posidonius had an extremely influential personality—he was reported to have a good sense of humor and was known as a man of dignity. He also developed a reputation as the most learned man in the world and was especially known for his dialectical skills, shrewd powers of observation, and love of poetry. Though he was extremely influential in his own time and for two centuries afterward, his writings disappeared at some point, and he is not mentioned after the second century c.e. Virtually all the important Roman philosophers and historians were influenced by Posidonius. His disciples and students included Phanias, Asclepiodotus, C. Velleins, C. Cotta, Q. Lucilius Balbus, and perhaps Marcus Junius Brutus. His influence on thought in the ancient world has been compared to that of Aristotle. He was the last compiler of the Greco-Roman heritage, furthered the development of Greek rationalism, and was influential in the development of Neoplatonism. Nevertheless, from the Renaissance through the nineteenth century, Posidonius was considered to be only a minor figure in the history of Stoicism. It was not until the beginning of the twentieth century that his influence was attested and classicists began to discover references to Posidonius in many of the writings of his time.

Bibliography

Dobson, J. F. “The Posidonius Myth.” Classical Quarterly 12 (1918): 179-191. Attacks the source criticism method of assessing Posidonius’s influence, suggesting that Posidonius’s achievements have been exaggerated.

Edelstein, Ludwig. “The Philosophical System of Posidonius.” American Journal of Philology 57 (1936): 286-325. Reconstructs the philosophical system of Posidonius from the existing fragments. Written by the foremost authority on Posidonius of the twentieth century.

Kidd, I. G. “Posidonius on Emotions.” In Problems in Stoicism, edited by A. A. Long. London: Athlone Press, 1971. Contains a detailed analysis of Posidonius’s modification of the standard Stoic conception of the emotions.

Mattingly, John Robert. “Cosmogony and Stereometry in Posidonian Physics.” Osiris 3 (1937): 558-583. Contains an extensive explication of the cosmological system developed by Posidonius.

Posidonius. Fragments, Volume 1. Translated by I. G. Kidd. 1972. Rev. ed. New York: Cambridge University Press, 1989. This edition contains sixty new readings, nearly eighty alterations to the apparatus criticus, corrections of errors, and cross-references to recently published works.

Posidonius. Fragments, Volume 2: Commentary. Translated by I. G. Kidd. New York: Cambridge University Press, 1992.

Posidonius. Translation of the Fragments, Volume 3. Translated by I. G. Kidd. New York: Cambridge University Press, 1999. The translations are accompanied by contextual introductions and explanatory notes, and a general introduction assesses the importance of Posidonius and his contribution. The order of fragments follows exactly that of the ancient texts collected and edited by L. Edelstein and I. G. Kidd in Posidonius Vol. 1 and completes (with Vol. 2, Commentary) what has become the definitive modern edition.

Rist, John Michael. Stoic Philosophy. Cambridge, England: Cambridge University Press, 1977. Contains a chapter devoted to the ethical system of Posidonius.

Solmsen, Friedrich. Cleanthes or Posidonius? The Basis of Stoic Physics. Amsterdam, Netherlands: Noord-Hollandsche Uitg. Mij., 1961. The best available discussion of the relative influence of Cleanthes and Posidonius on developments in Stoic thought concerning science and the relation between science and the cosmos.