Greek Stoic philosopher and scientist. Born c. 135 BCE in Apameia in Syria, died 50 BCE.
After studies with Panaitios in Athens, Poseidonios founded his own school on Rhodes. From there, he made excursions far afield, travelling all over the Mediterranean region. He took on many students, including Pompey and Cicero.
Only fragments of Poseidonios' works have been transmitted to the present, but they show him to have had a wide field of interests, stretching from the traditional Stoic disciplines of natural philosophy, ethics and logic to a wider spectrum of arts and sciences: astronomy, meteorology, mineralogy, oceanography, ethnography, history and geometry. With such a huge span, Poseidonios was unique in his time. He developed Stoicism by uniting philosophical theory with empirical knowledge - as he saw it, a theory's purpose was to uncover the underlying causes of phenomena, and any theory must therefore be empirically verified.