Posidonius
Encyclopedia
Posidonius "of Apameia
" (ὁ Ἀπαμεύς) or "of Rhodes
" (ὁ Ῥόδιος) (ca. 135 BCE - 51 BCE), was a Greek
Stoic
philosopher, politician
, astronomer
, geographer
, historian
and teacher
native to Apamea
, Syria
. He was acclaimed as the greatest polymath
of his age. None of his vast body of work can be read in its entirety today, as it exists only in fragments.
family in Apamea
, a Hellenistic city on the river Orontes in northern Syria
, and probably died in Rome
or Rhodes
.
Posidonius completed his higher education in Athens
, where he was a student of the aged Panaetius
, the head of the Stoic
school.
He settled around 95 BCE in Rhodes, a maritime state which had a reputation for scientific research, and became a citizen.
(presidents, having a six months tenure) of Rhodes. He served as an ambassador to Rome in 87 - 86 BCE, during the Marian
and Sullan
era.
Along with other Greek intellectuals, Posidonius favored Rome as the stabilizing power in a turbulent world. His connections to the Roman ruling class was for him not only politically important and sensible but was also important to his scientific research. His entry into government provided Posidonius with powerful connections to facilitate his travels to far away places, even beyond Roman control.
, Hispania
, Italy
, Sicily
, Dalmatia
, Gaul
, Liguria
, North Africa
, and on the eastern shores of the Adriatic.
In Hispania, on the Atlantic coast at Gades (the modern Cadiz
), 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 Celt
s. He left vivid descriptions of things he saw with his own eyes while among them: men who were paid to allow their throats to be slit for public amusement and the nailing of skulls as trophies to the doorways. 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 Celt
s which has since been lost, but which is referred to extensively (both directly and otherwise) in the works of Diodorus of Sicily, Strabo
, Caesar
and Tacitus
' Germania
.
, who was the son of his daughter and Menekrates of Nysa
, followed in his footsteps and continued Posidonius's school in Rhodes. Although little is known of the organization of his school, it is clear that Posidonius had a steady stream of Greek and Roman students.
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
(including meteorology
and physical geography
), 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 survive intact. All that we have found are fragments, although the titles and subjects of many of his books are known.
He accepted the Stoic categorization of philosophy into physics (natural philosophy, including metaphysics and theology), logic (including dialectic), 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 meat and blood, logic the bones and tendons holding the organism together, and finally ethics – the most important part – corresponding to the soul. His philosophical grand vision was that the universe itself was similarly interconnected, as if an organism, through cosmic "sympathy", in all respects from the development of the physical world to the history of humanity.
Although a firm Stoic, Posidonius was, like Panaetius and other Stoics of the middle period, eclectic. He followed not only the older Stoics, but Plato
and Aristotle
. Although it is not certain, Posidonius may have written a commentary on Plato's Timaeus
.
He was the first Stoic to depart from the orthodox doctrine that passions were faulty judgments and posit that Plato's view of the soul had been correct, namely that passions were inherent in human nature. In addition to the rational faculties, Posidonius taught that the human soul had faculties that were spirited (anger, desires for power, possessions, etc.) and desiderative (desires for sex and food). Ethics was the problem of how to deal with these passions and restore reason as the dominant faculty.
Posidonius upheld the Stoic doctrine of Logos
, which ultimately passed into Judeo-Christian
belief. Posidonius also affirmed the Stoic doctrine of the future conflagration.
, On the Circular Motions of the Celestial Bodies, the first chapter of the second book appearing to have been mostly copied from Posidonius.
Posidonius advanced the theory that the Sun emanated a vital force which permeated the world.
He attempted to measure the distance and size of the Sun
. In about 90 BCE Posidonius estimated the distance to the sun (see astronomical unit
) to be 9,893 times the Earth's radius, which was still too small by half. In measuring the size of the Sun, however, he reached a figure larger and more accurate than those proposed by other Greek astronomers and Aristarchus of Samos
.
Posidonius also calculated the size and distance of the Moon
.
Posidonius constructed an orrery
, possibly similar to the Antikythera mechanism
. Posidonius's orrery, according to Cicero
, exhibited the diurnal motions of the sun, moon, and the five known planets.
Posidonius’s fame beyond specialized philosophical circles had begun, at the latest, in the eighties with the publication of the work "about the ocean and the adjacent areas". This work was not only an overall representation of geographical questions according to current scientific knowledge, but it served to popularize his theories about the internal connections of the world, to show how all the forces had an effect on each other and how the interconnectedness applied also to human life, to the political just as to the personal spheres. In this work, Posidonius detailed his theory of the effect on a people’s character by the climate, which included his representation of the "geography of the races". This theory was not solely scientific, but also had political implications—his Roman readers were informed that the climatic central position of Italy was an essential condition of the Roman destiny to dominate the world. As a Stoic he did not, however, make a fundamental distinction between the civilized Romans as masters of the world and the less civilized peoples.
Posidonius measured the Earth
's circumference
by reference to the position of the star Canopus. As explained by Cleomedes, Posidonius observed Canopus on but never above the horizon at Rhodes, while at Alexandria
he saw it ascend as far as 7½ degrees above the horizon (the meridian arc
between the latitude of the two locales is actually 5 degrees 14 minutes). Since he thought Rhodes was 5,000 stadia
due north of Alexandria, and the difference in the star's elevation indicated the distance between the two locales was 1/48th of the circle, he multiplied 5,000 by 48 to arrive at a figure of 240,000 stadia for the circumference of the earth. While translating stadia into modern units of distance is problematic, as an ancient stadium could measure anywhere from about 157 to around 211 meters, it is generally thought that the stadium used by Posidonius was almost exactly 1/10 of a modern statute mile, near the middle of the ancient range. Thus Posidonius' measure of 240,000 stadia translates to 24,000 miles, not much short of the actual circumference of 24,901 miles.
Posidonius was informed in his approach to finding the Earth's circumference by Eratosthenes
, who a century earlier used the elevation of the sun at different latitudes to arrive at a figure of 250,000 stadia (which he rounded to 252,000 so that it would be divisible by 60). As with Posidonius, Eratosthenes' stadium is thought to have equated to 1/10 of a mile, so that his measure translates to 25,000 (or 25,200) miles. Both men's figures for the Earth's circumference were uncannily accurate, aided in part in each case by mutually compensating errors in measurement. However, Posidonius later revised his original calculation by correcting the distance between Rhodes and Alexandria to 3,750 stadia, resulting in a circumference of 180,000 Stadia, or 18,000 miles. Ptolemy
discussed and favored this revised figure of Posidonius over Eratosthenes in his Geographia, and during the Middle Ages
scholars divided into two camps regarding the circumference of the earth, identified with Eratosthenes' calculation on the one hand and Posidonius' 180,000-stadium measure on the other.
Like Pytheas
, Posidonius believed the tide
is caused by the Moon
. Posidonius was, however, wrong about the cause. Thinking that the Moon was a mixture of air and fire, he attributed the cause of the tides to the heat of the Moon, hot enough to cause the water to swell but not hot enough to evaporate it.
He recorded observations on both earthquakes and volcanoes, including accounts of the eruptions of the volcanoes in the Aeolian Islands
, north of Sicily
.
. He theorized on the causes of clouds, mist, wind, and rain as well as frost, hail, lightning, and rainbows.
. 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'.
. His history of the period 146 - 88 BCE is said to have filled 52 volumes. His Histories continue the account of the rise and expansion of Roman dominance, which he appears to have supported. Posidonius did not follow Polybius's more detached and factual style, for Posidonius saw events as caused by human psychology; while he understood human passions and follies, he did not pardon or excuse them in his historical writing, using his narrative skill in fact to enlist the readers' approval or condemnation.
For Posidonius "history" extended beyond the earth into the sky; humanity was not isolated each in its own political history, but was a part of the cosmos. His Histories were not, therefore, concerned with isolated political history of peoples and individuals, but they included discussions of all forces and factors (geographical factors, mineral resources, climate, nutrition), which let humans act and be a part of their environment. For example, Posidonius considered the climate of Arabia and the life-giving strength of the sun, tides (taken from his book on the oceans), and climatic theory to explain people’s ethnic or national characters.
Of Posidonius's work on tactics, The Art of War, the Greek historian Arrian
complained that it was written 'for experts', which suggests that Posidonius may have had first hand experience of military leadership or, perhaps, utilized knowledge he gained from his acquaintance with Pompey
.
In his own era, his writings on almost all the principal divisions of philosophy made Posidonius a renowned international figure throughout the Graeco-Roman world and he was widely cited by writers of his era, including Cicero, Livy
, Plutarch
, Strabo
(who called Posidonius "the most learned of all philosophers of my time"), Cleomedes, Seneca the Younger
, Diodorus Siculus
(who used Posidonius as a source for his Bibliotheca historia ["Historical Library"]), and others. Although his ornate and rhetorical style of writing passed out of fashion soon after his death, Posidonius was acclaimed during his life for his literary ability and as a stylist.
Posidonius was the major source of materials on the Celts of Gaul
and was profusely quoted by Timagenes
, Julius Caesar
, the Sicilian Greek Diodorus Siculus
, and the Greek geographer Strabo
.
Posidonius appears to have moved with ease among the upper echelons of Roman society as an ambassador from Rhodes. He associated with some of the leading figures of late republican Rome, including Cicero and Pompey, both of whom visited him in Rhodes. In his twenties, Cicero attended his lectures (77 BCE) and they continued to correspond. Cicero in his De Finibus closely followed Posidonius's presentation of Panaetius's ethical teachings. Posidonius met Pompey when he was Rhodes's ambassador in Rome and Pompey visited him in Rhodes twice, once in 66 BCE during his campaign against the pirates and again in 62 BCE during his eastern campaigns, and asked Posidonius to write his biography. As a gesture of respect and great honor, Pompey lowered his fasces
before Posidonius's door. Other Romans who visited Posidonius in Rhodes were Velleius, Cotta, and Lucilius
.
Ptolemy
was impressed by the sophistication of Posidonius's methods, which included correcting for the refraction of light passing through denser air near the horizon. Ptolemy's approval of Posidonius's result, rather than Eratosthenes's earlier and more correct figure, caused it to become the accepted value for the Earth's circumference for the next 1,500 years.
Posidonius fortified the Stoicism of the middle period with contemporary learning. Next to his teacher Panaetius, he did most, by writings and personal contacts, to spread Stoicism in the Roman world.
A century later, Seneca referred to Posidonius as one of those who had made the largest contribution to philosophy.
His influence on philosophical thinking lasted until the Middle Ages
, as is shown by citation in the Suda
, the massive medieval lexicon
.
At one time, scholars perceived Posidonius's influence in almost every subsequent writer, whether warranted or not. Today, Posidonius seems to be recognized as having had an inquiring and wide-ranging mind, not entirely original, but with a breadth of view that connected, in accordance with his underlying Stoic philosophy, all things and their causes and all knowledge into an overarching, unified world view.
The crater Posidonius
on the Moon
is named after him.
Apamea (Syria)
Apamea was a treasure city and stud-depot of the Seleucid kings, was capital of Apamene, on the right bank of the Orontes River. . Its site is found about to the northwest of Hama, Syria, overlooking the Ghab valley...
" (ὁ Ἀπαμεύς) or "of Rhodes
Rhodes
Rhodes is an island in Greece, located in the eastern Aegean Sea. It is the largest of the Dodecanese islands in terms of both land area and population, with a population of 117,007, and also the island group's historical capital. Administratively the island forms a separate municipality within...
" (ὁ Ῥόδιος) (ca. 135 BCE - 51 BCE), was a Greek
Greeks
The Greeks, also known as the Hellenes , are a nation and ethnic group native to Greece, Cyprus and neighboring regions. They also form a significant diaspora, with Greek communities established around the world....
Stoic
STOIC
STOIC was a variant of Forth.It started out at the MIT and Harvard Biomedical Engineering Centre in Boston, and was written in the mid 1970s by Jonathan Sachs...
philosopher, politician
Politician
A politician, political leader, or political figure is an individual who is involved in influencing public policy and decision making...
, astronomer
Astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...
, geographer
Geographer
A geographer is a scholar whose area of study is geography, the study of Earth's natural environment and human society.Although geographers are historically known as people who make maps, map making is actually the field of study of cartography, a subset of geography...
, historian
Historian
A historian is a person who studies and writes about the past and is regarded as an authority on it. Historians are concerned with the continuous, methodical narrative and research of past events as relating to the human race; as well as the study of all history in time. If the individual is...
and teacher
Teacher
A teacher or schoolteacher is a person who provides education for pupils and students . The role of teacher is often formal and ongoing, carried out at a school or other place of formal education. In many countries, a person who wishes to become a teacher must first obtain specified professional...
native to Apamea
Apamea
Apamea or Apameia is the name of several Hellenistic cities in western Asia, after Apama, the wife of Seleucus I Nicator:*Apamea , on the Tigris near the Euphrates, precise location unknown, now in Iraq...
, Syria
History of Syria
The history of Syria:*Prehistory and Ancient Near East: see Pre-history of the Southern Levant, Fertile Crescent, Ebla, Mitanni*Antiquity: see Syro-Hittite states, Greater Syria, Roman Syria...
. He was acclaimed as the greatest polymath
Polymath
A polymath is a person whose expertise spans a significant number of different subject areas. In less formal terms, a polymath may simply be someone who is very knowledgeable...
of his age. None of his vast body of work can be read in its entirety today, as it exists only in fragments.
Life
Posidonius, nicknamed "the Athlete", was born to a GreekGreeks
The Greeks, also known as the Hellenes , are a nation and ethnic group native to Greece, Cyprus and neighboring regions. They also form a significant diaspora, with Greek communities established around the world....
family in Apamea
Apamea (Syria)
Apamea was a treasure city and stud-depot of the Seleucid kings, was capital of Apamene, on the right bank of the Orontes River. . Its site is found about to the northwest of Hama, Syria, overlooking the Ghab valley...
, a Hellenistic city on the river Orontes in northern Syria
Syria
Syria , officially the Syrian Arab Republic , is a country in Western Asia, bordering Lebanon and the Mediterranean Sea to the West, Turkey to the north, Iraq to the east, Jordan to the south, and Israel to the southwest....
, and probably died in Rome
Rome
Rome is the capital of Italy and the country's largest and most populated city and comune, with over 2.7 million residents in . The city is located in the central-western portion of the Italian Peninsula, on the Tiber River within the Lazio region of Italy.Rome's history spans two and a half...
or Rhodes
Rhodes
Rhodes is an island in Greece, located in the eastern Aegean Sea. It is the largest of the Dodecanese islands in terms of both land area and population, with a population of 117,007, and also the island group's historical capital. Administratively the island forms a separate municipality within...
.
Posidonius completed his higher education in Athens
Athens
Athens , is the capital and largest city of Greece. Athens dominates the Attica region and is one of the world's oldest cities, as its recorded history spans around 3,400 years. Classical Athens was a powerful city-state...
, where he was a student of the aged Panaetius
Panaetius
Panaetius of Rhodes was a Stoic philosopher. He was a pupil of Diogenes of Babylon and Antipater of Tarsus in Athens, before moving to Rome where he did much to introduce Stoic doctrines to the city. After the death of Scipio in 129, he returned to the Stoic school in Athens, and was its last...
, the head of the Stoic
STOIC
STOIC was a variant of Forth.It started out at the MIT and Harvard Biomedical Engineering Centre in Boston, and was written in the mid 1970s by Jonathan Sachs...
school.
He settled around 95 BCE in Rhodes, a maritime state which had a reputation for scientific research, and became a citizen.
Political offices
In Rhodes, Posidonius actively took part in political life, and his high standing is apparent from the offices he held. He attained the highest public office as one of the PrytaneisPrytaneis
The Prytaneis were the executives of the boule of ancient Athens. The term is probably of pre-Greek origin ....
(presidents, having a six months tenure) of Rhodes. He served as an ambassador to Rome in 87 - 86 BCE, during the Marian
Gaius Marius
Gaius Marius was a Roman general and statesman. He was elected consul an unprecedented seven times during his career. He was also noted for his dramatic reforms of Roman armies, authorizing recruitment of landless citizens, eliminating the manipular military formations, and reorganizing the...
and Sullan
Lucius Cornelius Sulla
Lucius Cornelius Sulla Felix , known commonly as Sulla, was a Roman general and statesman. He had the rare distinction of holding the office of consul twice, as well as that of dictator...
era.
Along with other Greek intellectuals, Posidonius favored Rome as the stabilizing power in a turbulent world. His connections to the Roman ruling class was for him not only politically important and sensible but was also important to his scientific research. His entry into government provided Posidonius with powerful connections to facilitate his travels to far away places, even beyond Roman control.
Travels
After he had established himself in Rhodes, Posidonius made one or more journeys traveling throughout the Roman world and even beyond its boundaries to conduct scientific research. He traveled in GreeceGreece
Greece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....
, Hispania
Hispania
Another theory holds that the name derives from Ezpanna, the Basque word for "border" or "edge", thus meaning the farthest area or place. Isidore of Sevilla considered Hispania derived from Hispalis....
, Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
, Sicily
Sicily
Sicily is a region of Italy, and is the largest island in the Mediterranean Sea. Along with the surrounding minor islands, it constitutes an autonomous region of Italy, the Regione Autonoma Siciliana Sicily has a rich and unique culture, especially with regard to the arts, music, literature,...
, Dalmatia
Dalmatia
Dalmatia is a historical region on the eastern coast of the Adriatic Sea. It stretches from the island of Rab in the northwest to the Bay of Kotor in the southeast. The hinterland, the Dalmatian Zagora, ranges from fifty kilometers in width in the north to just a few kilometers in the south....
, Gaul
Gaul
Gaul was a region of Western Europe during the Iron Age and Roman era, encompassing present day France, Luxembourg and Belgium, most of Switzerland, the western part of Northern Italy, as well as the parts of the Netherlands and Germany on the left bank of the Rhine. The Gauls were the speakers of...
, Liguria
Liguria
Liguria is a coastal region of north-western Italy, the third smallest of the Italian regions. Its capital is Genoa. It is a popular region with tourists for its beautiful beaches, picturesque little towns, and good food.-Geography:...
, North Africa
North Africa
North Africa or Northern Africa is the northernmost region of the African continent, linked by the Sahara to Sub-Saharan Africa. Geopolitically, the United Nations definition of Northern Africa includes eight countries or territories; Algeria, Egypt, Libya, Morocco, South Sudan, Sudan, Tunisia, and...
, and on the eastern shores of the Adriatic.
In Hispania, on the Atlantic coast at Gades (the modern Cadiz
Cádiz
Cadiz is a city and port in southwestern Spain. It is the capital of the homonymous province, one of eight which make up the autonomous community of Andalusia....
), Posidonius could observe tides much higher than in his native Mediterranean. He wrote that daily tides are related to the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
's orbit, while tidal heights vary with the cycles of the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
, and he hypothesized about yearly tidal cycles synchronized with the equinoxes and solstices.
In Gaul, he studied the Celt
Celt
The Celts were a diverse group of tribal societies in Iron Age and Roman-era Europe who spoke Celtic languages.The earliest archaeological culture commonly accepted as Celtic, or rather Proto-Celtic, was the central European Hallstatt culture , named for the rich grave finds in Hallstatt, Austria....
s. He left vivid descriptions of things he saw with his own eyes while among them: men who were paid to allow their throats to be slit for public amusement and the nailing of skulls as trophies to the doorways. 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 Celt
Celt
The Celts were a diverse group of tribal societies in Iron Age and Roman-era Europe who spoke Celtic languages.The earliest archaeological culture commonly accepted as Celtic, or rather Proto-Celtic, was the central European Hallstatt culture , named for the rich grave finds in Hallstatt, Austria....
s which has since been lost, but which is referred to extensively (both directly and otherwise) in the works of Diodorus of Sicily, Strabo
Strabo
Strabo, also written Strabon was a Greek historian, geographer and philosopher.-Life:Strabo was born to an affluent family from Amaseia in Pontus , a city which he said was situated the approximate equivalent of 75 km from the Black Sea...
, Caesar
Caesar
-People:* Julius Caesar , Roman general and dictator* Augustus Caesar , adoptive son of the above and first Roman Emperor* Gaius Julius Caesar , father of the dictator...
and Tacitus
Tacitus
Publius Cornelius Tacitus was a senator and a historian of the Roman Empire. The surviving portions of his two major works—the Annals and the Histories—examine the reigns of the Roman Emperors Tiberius, Claudius, Nero and those who reigned in the Year of the Four Emperors...
' Germania
Germania (book)
The Germania , written by Gaius Cornelius Tacitus around 98, is an ethnographic work on the Germanic tribes outside the Roman Empire.-Contents:...
.
School
Posidonius's extensive writings and lectures gave him authority as a scholar and made him famous everywhere in the Graeco-Roman world, and a school grew around him in Rhodes. His grandson JasonJason of Nysa
Jason of Nysa, a Stoic philosopher, son of Menecrates, and, on his mother's side, grandson of Posidonius, of whom also he was the disciple and successor at the Stoic school at Rhodes. He therefore flourished after the middle of the 1st century BC...
, who was the son of his daughter and Menekrates of Nysa
Nysa, Anatolia
Nysa was an ancient city of Caria in Anatolia, whose remnants are now in the Sultanhisar district of Aydın Province of Turkey, east of the Ionian city of Ephesus....
, followed in his footsteps and continued Posidonius's school in Rhodes. Although little is known of the organization of his school, it is clear that Posidonius had a steady stream of Greek and Roman students.
Partial scope of writings
Posidonius was celebrated as a polymathPolymath
A polymath is a person whose expertise spans a significant number of different subject areas. In less formal terms, a polymath may simply be someone who is very knowledgeable...
throughout the Graeco-Roman world because he came near to mastering all the knowledge of his time, similar to Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...
and Eratosthenes
Eratosthenes
Eratosthenes of Cyrene was a Greek mathematician, poet, athlete, geographer, astronomer, and music theorist.He was the first person to use the word "geography" and invented the discipline of geography as we understand it...
. 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
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
(including meteorology
Meteorology
Meteorology is the interdisciplinary scientific study of the atmosphere. Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the 18th century. The 19th century saw breakthroughs occur after observing networks developed across several countries...
and physical geography
Physical geography
Physical geography is one of the two major subfields of geography. Physical geography is that branch of natural science which deals with the study of processes and patterns in the natural environment like the atmosphere, biosphere and geosphere, as opposed to the cultural or built environment, the...
), astronomy
Astronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...
, astrology
Astrology
Astrology consists of a number of belief systems which hold that there is a relationship between astronomical phenomena and events in the human world...
and divination
Divination
Divination is the attempt to gain insight into a question or situation by way of an occultic standardized process or ritual...
, seismology
Seismology
Seismology is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other planet-like bodies. The field also includes studies of earthquake effects, such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, oceanic,...
, geology
Geology
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...
and mineralogy
Mineralogy
Mineralogy is the study of chemistry, crystal structure, and physical properties of minerals. Specific studies within mineralogy include the processes of mineral origin and formation, classification of minerals, their geographical distribution, as well as their utilization.-History:Early writing...
, hydrology
Hydrology
Hydrology is the study of the movement, distribution, and quality of water on Earth and other planets, including the hydrologic cycle, water resources and environmental watershed sustainability...
, botany
Botany
Botany, plant science, or plant biology is a branch of biology that involves the scientific study of plant life. Traditionally, botany also included the study of fungi, algae and viruses...
, ethics
Ethics
Ethics, also known as moral philosophy, is a branch of philosophy that addresses questions about morality—that is, concepts such as good and evil, right and wrong, virtue and vice, justice and crime, etc.Major branches of ethics include:...
, logic
Logic
In philosophy, Logic is the formal systematic study of the principles of valid inference and correct reasoning. Logic is used in most intellectual activities, but is studied primarily in the disciplines of philosophy, mathematics, semantics, and computer science...
, mathematics
Mathematics
Mathematics is the study of quantity, space, structure, and change. Mathematicians seek out patterns and formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proofs, which are arguments sufficient to convince other mathematicians of their validity...
, history
History
History is the discovery, collection, organization, and presentation of information about past events. History can also mean the period of time after writing was invented. Scholars who write about history are called historians...
, natural history
Natural history
Natural history is the scientific research of plants or animals, leaning more towards observational rather than experimental methods of study, and encompasses more research published in magazines than in academic journals. Grouped among the natural sciences, natural history is the systematic study...
, anthropology
Anthropology
Anthropology is the study of humanity. It has origins in the humanities, the natural sciences, and the social sciences. The term "anthropology" is from the Greek anthrōpos , "man", understood to mean mankind or humanity, and -logia , "discourse" or "study", and was first used in 1501 by German...
, and tactics. His studies were major investigations into their subjects, although not without errors.
None of his works survive intact. All that we have found are fragments, although the titles and subjects of many of his books are known.
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 (natural philosophy, including metaphysics and theology), logic (including dialectic), 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 meat and blood, logic the bones and tendons holding the organism together, and finally ethics – the most important part – corresponding to the soul. His philosophical grand vision was that the universe itself was similarly interconnected, as if an organism, through cosmic "sympathy", in all respects from the development of the physical world to the history of humanity.
Although a firm Stoic, Posidonius was, like Panaetius and other Stoics of the middle period, eclectic. He followed not only the older Stoics, but Plato
Plato
Plato , was a Classical Greek philosopher, mathematician, student of Socrates, writer of philosophical dialogues, and founder of the Academy in Athens, the first institution of higher learning in the Western world. Along with his mentor, Socrates, and his student, Aristotle, Plato helped to lay the...
and Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...
. Although it is not certain, Posidonius may have written a commentary on Plato's Timaeus
Timaeus (dialogue)
Timaeus is one of Plato's dialogues, mostly in the form of a long monologue given by the title character, written circa 360 BC. The work puts forward speculation on the nature of the physical world and human beings. It is followed by the dialogue Critias.Speakers of the dialogue are Socrates,...
.
He was the first Stoic to depart from the orthodox doctrine that passions were faulty judgments and posit that Plato's view of the soul had been correct, namely that passions were inherent in human nature. In addition to the rational faculties, Posidonius taught that the human soul had faculties that were spirited (anger, desires for power, possessions, etc.) and desiderative (desires for sex and food). Ethics was the problem of how to deal with these passions and restore reason as the dominant faculty.
Posidonius upheld the Stoic doctrine of Logos
Logos
' is an important term in philosophy, psychology, rhetoric and religion. Originally a word meaning "a ground", "a plea", "an opinion", "an expectation", "word," "speech," "account," "reason," it became a technical term in philosophy, beginning with Heraclitus ' is an important term in...
, which ultimately passed into Judeo-Christian
Judeo-Christian
Judeo-Christian is a term used in the United States since the 1940s to refer to standards of ethics said to be held in common by Judaism and Christianity, for example the Ten Commandments...
belief. Posidonius also affirmed the Stoic doctrine of the future conflagration.
Physics
In Stoic physics, Posidonius advocated a theory of cosmic "sympathy" (sumpatheia), 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, even those that were temporally and spatially separate. Although his teacher Panaetius had doubted divination, Posidonius used the theory of cosmic sympathy to support his belief in divination - whether through astrology or prophetic dreams - as a kind of scientific prediction.Astronomy
Some fragments of his writings on astronomy survive through the treatise by CleomedesCleomedes
Cleomedes was a Greek astronomer who is known chiefly for his book On the Circular Motions of the Celestial Bodies.-Placing his work chronologically:...
, On the Circular Motions of the Celestial Bodies, the first chapter of the second book appearing to have been mostly copied from Posidonius.
Posidonius advanced the theory that the Sun emanated a vital force which permeated the world.
He attempted to measure the distance and size of the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
. In about 90 BCE Posidonius estimated the distance to the sun (see astronomical unit
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
) to be 9,893 times the Earth's radius, which was still too small by half. In measuring the size of the Sun, however, he reached a figure larger and more accurate than those proposed by other Greek astronomers and Aristarchus of Samos
Aristarchus of Samos
Aristarchus, or more correctly Aristarchos , was a Greek astronomer and mathematician, born on the island of Samos, in Greece. He presented the first known heliocentric model of the solar system, placing the Sun, not the Earth, at the center of the known universe...
.
Posidonius also calculated the size and distance of the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
.
Posidonius constructed an orrery
Orrery
An orrery is a mechanical device that illustrates the relative positions and motions of the planets and moons in the Solar System in a heliocentric model. Though the Greeks had working planetaria, the first orrery that was a planetarium of the modern era was produced in 1704, and one was presented...
, possibly similar to the Antikythera mechanism
Antikythera mechanism
The Antikythera mechanism is an ancient mechanical computer designed to calculate astronomical positions. It was recovered in 1900–1901 from the Antikythera wreck. Its significance and complexity were not understood until decades later. Its time of construction is now estimated between 150 and 100...
. Posidonius's orrery, according to Cicero
Cicero
Marcus Tullius Cicero , was a Roman philosopher, statesman, lawyer, political theorist, and Roman constitutionalist. He came from a wealthy municipal family of the equestrian order, and is widely considered one of Rome's greatest orators and prose stylists.He introduced the Romans to the chief...
, exhibited the diurnal motions of the sun, moon, and the five known planets.
Geography, ethnology and geology
Posidonius measured the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
's circumference
Circumference
The circumference is the distance around a closed curve. Circumference is a special perimeter.-Circumference of a circle:The circumference of a circle is the length around it....
by reference to the position of the star Canopus. As explained by Cleomedes, Posidonius observed Canopus on but never above the horizon at Rhodes, while at Alexandria
Alexandria
Alexandria is the second-largest city of Egypt, with a population of 4.1 million, extending about along the coast of the Mediterranean Sea in the north central part of the country; it is also the largest city lying directly on the Mediterranean coast. It is Egypt's largest seaport, serving...
he saw it ascend as far as 7½ degrees above the horizon (the meridian arc
Meridian arc
In geodesy, a meridian arc measurement is a highly accurate determination of the distance between two points with the same longitude. Two or more such determinations at different locations then specify the shape of the reference ellipsoid which best approximates the shape of the geoid. This...
between the latitude of the two locales is actually 5 degrees 14 minutes). Since he thought Rhodes was 5,000 stadia
Stadion (unit of length)
The stadion, Latinized as stadium and anglicized as stade, is an ancient Greek unit of length. According to Herodotus, one stade is equal to 600 feet. However, there were several different lengths of “feet”, depending on the country of origin....
due north of Alexandria, and the difference in the star's elevation indicated the distance between the two locales was 1/48th of the circle, he multiplied 5,000 by 48 to arrive at a figure of 240,000 stadia for the circumference of the earth. While translating stadia into modern units of distance is problematic, as an ancient stadium could measure anywhere from about 157 to around 211 meters, it is generally thought that the stadium used by Posidonius was almost exactly 1/10 of a modern statute mile, near the middle of the ancient range. Thus Posidonius' measure of 240,000 stadia translates to 24,000 miles, not much short of the actual circumference of 24,901 miles.
Posidonius was informed in his approach to finding the Earth's circumference by Eratosthenes
Eratosthenes
Eratosthenes of Cyrene was a Greek mathematician, poet, athlete, geographer, astronomer, and music theorist.He was the first person to use the word "geography" and invented the discipline of geography as we understand it...
, who a century earlier used the elevation of the sun at different latitudes to arrive at a figure of 250,000 stadia (which he rounded to 252,000 so that it would be divisible by 60). As with Posidonius, Eratosthenes' stadium is thought to have equated to 1/10 of a mile, so that his measure translates to 25,000 (or 25,200) miles. Both men's figures for the Earth's circumference were uncannily accurate, aided in part in each case by mutually compensating errors in measurement. However, Posidonius later revised his original calculation by correcting the distance between Rhodes and Alexandria to 3,750 stadia, resulting in a circumference of 180,000 Stadia, or 18,000 miles. Ptolemy
Ptolemy
Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...
discussed and favored this revised figure of Posidonius over Eratosthenes in his Geographia, and during the Middle Ages
Middle Ages
The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...
scholars divided into two camps regarding the circumference of the earth, identified with Eratosthenes' calculation on the one hand and Posidonius' 180,000-stadium measure on the other.
Like Pytheas
Pytheas
Pytheas of Massalia or Massilia , was a Greek geographer and explorer from the Greek colony, Massalia . He made a voyage of exploration to northwestern Europe at about 325 BC. He travelled around and visited a considerable part of Great Britain...
, Posidonius believed the tide
Tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....
is caused by the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
. Posidonius was, however, wrong about the cause. Thinking that the Moon was a mixture of air and fire, he attributed the cause of the tides to the heat of the Moon, hot enough to cause the water to swell but not hot enough to evaporate it.
He recorded observations on both earthquakes and volcanoes, including accounts of the eruptions of the volcanoes in the Aeolian Islands
Aeolian Islands
The Aeolian Islands or Lipari Islands are a volcanic archipelago in the Tyrrhenian Sea north of Sicily, named after the demigod of the winds Aeolus. The locals residing on the islands are known as Eolians . The Aeolian Islands are a popular tourist destination in the summer, and attract up to...
, north of Sicily
Sicily
Sicily is a region of Italy, and is the largest island in the Mediterranean Sea. Along with the surrounding minor islands, it constitutes an autonomous region of Italy, the Regione Autonoma Siciliana Sicily has a rich and unique culture, especially with regard to the arts, music, literature,...
.
Meteorology
Posidonius in his writings on meteorology followed AristotleAristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...
. He theorized on the causes of clouds, mist, wind, and rain as well as frost, hail, lightning, and rainbows.
Mathematics
Posidonius was one of the first people to attempt to prove Euclid's fifth postulate of geometryParallel postulate
In geometry, the parallel postulate, also called Euclid's fifth postulate because it is the fifth postulate in Euclid's Elements, is a distinctive axiom in Euclidean 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'.
History and tactics
In his Histories, Posidonius continued the World History of PolybiusPolybius
Polybius , Greek ) was a Greek historian of the Hellenistic Period noted for his work, The Histories, which covered the period of 220–146 BC in detail. The work describes in part the rise of the Roman Republic and its gradual domination over Greece...
. His history of the period 146 - 88 BCE is said to have filled 52 volumes. His Histories continue the account of the rise and expansion of Roman dominance, which he appears to have supported. Posidonius did not follow Polybius's more detached and factual style, for Posidonius saw events as caused by human psychology; while he understood human passions and follies, he did not pardon or excuse them in his historical writing, using his narrative skill in fact to enlist the readers' approval or condemnation.
For Posidonius "history" extended beyond the earth into the sky; humanity was not isolated each in its own political history, but was a part of the cosmos. His Histories were not, therefore, concerned with isolated political history of peoples and individuals, but they included discussions of all forces and factors (geographical factors, mineral resources, climate, nutrition), which let humans act and be a part of their environment. For example, Posidonius considered the climate of Arabia and the life-giving strength of the sun, tides (taken from his book on the oceans), and climatic theory to explain people’s ethnic or national characters.
Of Posidonius's work on tactics, The Art of War, the Greek historian Arrian
Arrian
Lucius Flavius Arrianus 'Xenophon , known in English as Arrian , and Arrian of Nicomedia, was a Roman historian, public servant, a military commander and a philosopher of the 2nd-century Roman period...
complained that it was written 'for experts', which suggests that Posidonius may have had first hand experience of military leadership or, perhaps, utilized knowledge he gained from his acquaintance with Pompey
Pompey
Gnaeus Pompeius Magnus, also known as Pompey or Pompey the Great , was a military and political leader of the late Roman Republic...
.
Reputation and influence
Livy
Titus Livius — known as Livy in English — was a Roman historian who wrote a monumental history of Rome and the Roman people. Ab Urbe Condita Libri, "Chapters from the Foundation of the City," covering the period from the earliest legends of Rome well before the traditional foundation in 753 BC...
, Plutarch
Plutarch
Plutarch then named, on his becoming a Roman citizen, Lucius Mestrius Plutarchus , c. 46 – 120 AD, was a Greek historian, biographer, essayist, and Middle Platonist known primarily for his Parallel Lives and Moralia...
, Strabo
Strabo
Strabo, also written Strabon was a Greek historian, geographer and philosopher.-Life:Strabo was born to an affluent family from Amaseia in Pontus , a city which he said was situated the approximate equivalent of 75 km from the Black Sea...
(who called Posidonius "the most learned of all philosophers of my time"), Cleomedes, Seneca the Younger
Seneca the Younger
Lucius Annaeus Seneca was a Roman Stoic philosopher, statesman, dramatist, and in one work humorist, of the Silver Age of Latin literature. He was tutor and later advisor to emperor Nero...
, Diodorus Siculus
Diodorus Siculus
Diodorus Siculus was a Greek historian who flourished between 60 and 30 BC. According to Diodorus' own work, he was born at Agyrium in Sicily . With one exception, antiquity affords no further information about Diodorus' life and doings beyond what is to be found in his own work, Bibliotheca...
(who used Posidonius as a source for his Bibliotheca historia ["Historical Library"]), and others. Although his ornate and rhetorical style of writing passed out of fashion soon after his death, Posidonius was acclaimed during his life for his literary ability and as a stylist.
Posidonius was the major source of materials on the Celts of Gaul
Gaul
Gaul was a region of Western Europe during the Iron Age and Roman era, encompassing present day France, Luxembourg and Belgium, most of Switzerland, the western part of Northern Italy, as well as the parts of the Netherlands and Germany on the left bank of the Rhine. The Gauls were the speakers of...
and was profusely quoted by Timagenes
Timagenes
Timagenes was a Greek writer, historian and teacher of rhetoric. He came from Alexandria, was captured by Romans in 55 BC and taken to Rome, where he was purchased by Faustus Cornelius Sulla, son of Sulla. It is said that Timagenes had a falling-out with emperor Augustus, whereupon he destroyed...
, Julius Caesar
Julius Caesar
Gaius Julius Caesar was a Roman general and statesman and a distinguished writer of Latin prose. He played a critical role in the gradual transformation of the Roman Republic into the Roman Empire....
, the Sicilian Greek Diodorus Siculus
Diodorus Siculus
Diodorus Siculus was a Greek historian who flourished between 60 and 30 BC. According to Diodorus' own work, he was born at Agyrium in Sicily . With one exception, antiquity affords no further information about Diodorus' life and doings beyond what is to be found in his own work, Bibliotheca...
, and the Greek geographer Strabo
Strabo
Strabo, also written Strabon was a Greek historian, geographer and philosopher.-Life:Strabo was born to an affluent family from Amaseia in Pontus , a city which he said was situated the approximate equivalent of 75 km from the Black Sea...
.
Posidonius appears to have moved with ease among the upper echelons of Roman society as an ambassador from Rhodes. He associated with some of the leading figures of late republican Rome, including Cicero and Pompey, both of whom visited him in Rhodes. In his twenties, Cicero attended his lectures (77 BCE) and they continued to correspond. Cicero in his De Finibus closely followed Posidonius's presentation of Panaetius's ethical teachings. Posidonius met Pompey when he was Rhodes's ambassador in Rome and Pompey visited him in Rhodes twice, once in 66 BCE during his campaign against the pirates and again in 62 BCE during his eastern campaigns, and asked Posidonius to write his biography. As a gesture of respect and great honor, Pompey lowered his fasces
Fasces
Fasces are a bundle of wooden sticks with an axe blade emerging from the center, which is an image that traditionally symbolizes summary power and jurisdiction, and/or "strength through unity"...
before Posidonius's door. Other Romans who visited Posidonius in Rhodes were Velleius, Cotta, and Lucilius
Lucilius
Lucilius is the nomen of the gens Lucilia of ancient Rome.*Gaius Lucilius, satirist 2nd century BC. Lucilius was credited by Horace and others with originating the genre of satire.*Lucilius Junior, friend and correspondent of the younger Seneca....
.
Ptolemy
Ptolemy
Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...
was impressed by the sophistication of Posidonius's methods, which included correcting for the refraction of light passing through denser air near the horizon. Ptolemy's approval of Posidonius's result, rather than Eratosthenes's earlier and more correct figure, caused it to become the accepted value for the Earth's circumference for the next 1,500 years.
Posidonius fortified the Stoicism of the middle period with contemporary learning. Next to his teacher Panaetius, he did most, by writings and personal contacts, to spread Stoicism in the Roman world.
A century later, Seneca referred to Posidonius as one of those who had made the largest contribution to philosophy.
His influence on philosophical thinking lasted until the Middle Ages
Middle Ages
The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...
, as is shown by citation in the Suda
Suda
The Suda or Souda is a massive 10th century Byzantine encyclopedia of the ancient Mediterranean world, formerly attributed to an author called Suidas. It is an encyclopedic lexicon, written in Greek, with 30,000 entries, many drawing from ancient sources that have since been lost, and often...
, the massive medieval lexicon
Lexicon
In linguistics, the lexicon of a language is its vocabulary, including its words and expressions. A lexicon is also a synonym of the word thesaurus. More formally, it is a language's inventory of lexemes. Coined in English 1603, the word "lexicon" derives from the Greek "λεξικόν" , neut...
.
At one time, scholars perceived Posidonius's influence in almost every subsequent writer, whether warranted or not. Today, Posidonius seems to be recognized as having had an inquiring and wide-ranging mind, not entirely original, but with a breadth of view that connected, in accordance with his underlying Stoic philosophy, all things and their causes and all knowledge into an overarching, unified world view.
The crater Posidonius
Posidonius (crater)
Posidonius is a lunar impact crater that is located on the western edge of Mare Serenitatis, to the south of Lacus Somniorum. The crater Chacornac is attached to the southeast rim, and to the north is Daniell....
on the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
is named after him.
See also
- Twin Study
- Freeman,Phillip,The Philosopher and the Druids: A Journey Among The Ancient Celts, Simon and Schuster,2006.
- William B. Irvine, (2008), A Guide to the Good Life: The Ancient Art of Stoic Joy. Oxford University Press. ISBN 978-0-19-537461-2 — Discussion of his work and influence.