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Poseidonius of Rhodes, Weird Stoicism, and ‘Cosmic Religion’

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[Thanks to the howling gale and pounding rain, supplied by Dartmoor free of charge, which provide the soundtrack to this episode]

Poseidonius of Rhodes was a highly-influential Stoic of the so-called ‘middle Stoicism’, and many scholars have seen in him the propounder of a number of doctrines of crucial importance for the development of western esotericism, including the doctrine of kosmic sympathy (and influential theories of divination based in that doctrine), philosophical astrology, arithmological theories, and more. But other scholars reckon he was a plain-old scientist and philosopher with nothing particularly esoteric going on.

We look at the evidence and argue that regular Stoicism was already pretty weird, but also that Poseidonius probably had more weirdness going on than common-or-garden Stoicism, even if we can’t always say for sure what exactly he taught on a given subject, or how crucial his teachings were to the transmission of the various ‘esoteric’ ideas which we know he was interested in.

Works Cited in this Episode:


Get your Poseidonian fragments from Edelstein and Kidd:

  • Posidonius: Volume 1, The Fragments. Cambridge University Press, Cambridge, 1989.
  • Posidonius: Volume 2, The Commentary. 2 Vols. Cambridge University Press, Cambridge, 1988.
  • Posidonius: Volume 3, The Translation of the Fragments. Cambridge University Press, Cambridge, 1999.

Augustine De civ. dei V.2 and 5.

Boethius Commentum in Ciceronis Topica 20.77.

Chryssipus, cited in the Plutarchian or Pseudo-Plutarchian On Fate cp. 11 p. 574 d: τὸν κόσμον συμπνοῦν καὶ συμπαθῆ αὐτὸν αὐτῷ ὄντα. J. Arnim, editor. Stoicorum Veterum Fragmenta. Teubner, Leipzig, 1905-24. 4 vols. Fr. 912, Vol. II, p. 264.

Cicero, Hortensius, Frag. 97 Müller, 36 . Quoted by Augustine, De trinitate 14.19.26.

Diogenes Læertius on the Stoic soul as part of the divine pneuma: 7 143 s.v. Zēnōn. We cite the translation of Mensch in Diogenes Laertius. Lives of the Eminent Philosophers. Oxford University Press, Oxford, 2018.

Galen, evidence for the ‘return to Plato’ in Poseidonius: De Placitis Hippocratis et Platonis, mainly books 3, 4, 5 (up to 336.15) in the edition of De Lacy (Corpus Medicorum Graecorum, 5, 4, l, 2), Berlin, 1978-1984.


  • On the Celts: frr. 16 & 55.
  • Ekpyrōsis rejected by Panætius and Beothus of Sidon, accepted by Poseidonius: fr. 99.
  • God’s ousia is the whole kosmos: fr. 20,
  • but his nous or hegemonikon is the heavens, whereas in the earth he is present only as hexis,: frr. 21 & 23.
  • On astral afterlife: Sextus Empiricus Adv. Phys. 1 72 (no Kidd/Edelstein fragment number).

Sextus Empiricus preserves a fragment of Poseidonius (Adv. Math. 7.93 = Poseidonius fr. 85) where he says φησιν ὁ Ποσειδωνιος τον Πλατωνος Τιμαιον ἐξηγουμενος; this looks a lot like he is reading a Poseidonian Commentary on the Timæus, but could just mean ‘Poseidonius says, interpreting Plato’s Timæus’.


John Dillon. The Middle Platonists: A Study of Platonism 80 BC to AD 220. Duckworth, London, 1977. We quote p. xiv. Quotation of Sextus Adv. Phys. 1 72: p. 111. The doctrine of the Sextus passage is essentially that of Plutarch in the myth of the De Genio Socratis: p. 112.

André-Jean Festugière. La révélation d’Hermes Trismegiste. J. Gabalda, Paris, 1944-1954. 4 vols. We cite II, p. xiii.

René Hoven. Stoïcisme et Stoïciens face au probleme de l’au-delà. Les Belles Lettres, Paris, 1971.

Gretchen Reydams-Schils. Demiurge and Providence: Stoic and Platonist Readings of Plato’s Timaeus. Brepols, 1999; we quote p. 86.

Frank Egleston Robbins. Posidonius and the Sources of Pythagorean Arithmology. Classical Philology, 15(4):309-22, Oct. 1920; we quote p. 322.

August Schmekel. Die Philosophie der mittleren Stoa in ihrem geschichtlichen Zusammenhange dargestellt. Weidmannsche Buchhandlung, Berlin, 1892.

Recommended Reading:

Marie Laranque. Poseidonios d’Apamee: Essai de mise au point. Presses Universitaires de France, Paris, 1964.

A. Long. Hellenistic Philosophy: Stoics, Epicureans, Sceptics, London, 1974.

K. Reinhardt. Poseidonios. Real-Encyclopaedie der klassischen Altertumswissenschaft, 22(1): cols. 570.28-624.11.