This brilliant development of Stoicism continued in a completely different way with the Syrian Posidonius of Apamea (135-51). A great traveler and great observer of nature, he visited all the coasts of the Mediterranean, Sicily, the coasts of the Adriatic, Narbonensis Gaul, the coasts of Spain as far as the Atlantic, where he observed the phenomenon of the tides. Settled in Rhodes after 104, he was head of the school there, at the same time as he occupied the important political function of prytane. His relations with Rome were constant; during the Mithridatic War, when Rhodes, almost alone in the East, had remained on the Roman side, he went to Rome as an embassy to ask for help. Pompey was his personal friend and visited him several times in Rhodes; The memory of their conversations was preserved by Cicero, Pliny the Elder and Plutarch; Pompey heard him defend philosophy against the usurpations of the rhetorician Hermagoras: the philosopher must reserve general theses for himself and the orator be content with hypotheses. 20 He was also the friend and master of Cicero who stayed in Rhodes in 77. Like Panetius, Posidonius adhered wholeheartedly to the Roman party; the historian Polybius, who sees in Roman domination the conclusion of history, makes their link; Panetius is the friend of Polybius, and Posidonius continued his history.
Of his philosophical works no more than of his scientific, mathematical, historical and geographical works, of a work whose scope is comparable only to that of Aristotle’s encyclopedia, nothing remains. To reconstruct his thought, we must use Cicero’s book II of the treatise On the Nature of the Gods, book I of the Tusculanae, and the treatise On Divination; Galen makes known to us his polemic against Chrysippus on the nature of the passions; Seneca, in the Natural Questions, used a meteorological work by Asclepiodotus of Nicaea, whose ideas go back to Posidonius; Strabo often cites him in his Geography, and Cleomedes, in his Theory of Circular Motion, draws inspiration from him; let us finally add some data from Proclus on his mathematical thought in his Commentary on Euclid.
All this is very fragmentary, and the very important question of the meaning and historical scope of Posidonius’ work remains highly controversial, especially since Heinze, in 1892, in his work on Xenocrates, and Norden, in 1903, in his Commentary on the VIth Book of the Aeneid, believed they recognized the influence of Posidonius on the eschatological myth of the VIth Book of the Aeneid by Virgil and on the one that ends Plutarch’s treatise On the Face Seen in the Moon. These entirely Platonic myths, the last of which especially represents the purified soul rising towards the celestial regions, compared with the Dream of Scipio, in which Cicero shows the soul, after death, contemplating the order of the world, compared also with the fact that Posidonius, much more clearly still than Panetius, returned, against Stoicism, to the Platonic theory of the soul, have led to seeing in Posidonius a thinker above all religious, author of a synthesis between Stoicism and Platonism, and the true initiator of Neo-Platonism. Starting from this hypothesis, we wanted to see the traces of Posidonius’ thought, wherever we find this sort of mystical asceticism, which abounds at the end of Antiquity and which supposes a conception of the soul and a conception of the world: the soul composed of two elements, one pure, the other impure, which defiles the first and from which the first must free itself; a world made, in the image of this soul, of a pure region (heaven or God) where the spirit must reach and of an impure region in which it finds itself; such, the numerous ascetic passages of the work of Philo of Alexandria (whose treatise On the Creation of the World would come from a Commentary on the Timaeus of Posidonius), those of Seneca and the cosmological conceptions of the small treatise On the World which is found in the collection of the works of Aristotle.
If we stick to what we certainly know, we will be careful not to make Posidonius the author responsible for these beliefs – which we will see creeping in under so many forms from our era.
The Posidonian image of the universe emerges clearly from Book II of Cicero’s treatise On the Nature of the Gods, as soon as we accept the fine critical analysis that Reinhardt made of it. He showed, by comparing this book with the corresponding passages of Sextus Empiricus, that Cicero used two Stoic treatises of very different character, the first, a development of a school theory, made of syllogisms accumulated and constantly repeated in several forms, the second of a completely different style, giving great place to intuition and experience, without using syllogisms; Every time Cicero uses this treatise, no corresponding text is found in Sextus. Such are Chapters 17 to 22 and 39 to 60, which form a whole, a treatise on providence; providence is not proven there as a corollary of the principles, but grasped in a direct vision in the whole of the ascending scale of beings from the inorganic to the organic and to man, not without exotic details which make the picture very lively. Similarly, in chapters 11, 15 and 16, it is easy to see that the principle of providence is defined less as a reason (in the manner of ancient stoicism) than as a physical agent, heat, which manifests itself in particular in the stars; finally in chapters 32 to 37 we find the same general view of the gradation of living things, passing from the particular life of plants to the universal life of the earth, from which it comes. According to Reinhardt’s apt formula, in ancient Stoicism, “reason is organic; there the organic is rational”; the divine fire is no longer primarily a reason, it is an organic force (vis vitalis, says Seneca).
The physics of Posidonius would therefore be above all a dynamism insisting on the expansion of life and the gradual complication of living beings. We thus conceive in their full sense the definition of the world that Diogenes Laërtius (VII, 158) attributes to Posidonius: a system made of heaven, earth and the natures which are in them. In such a system the unity of the world, unfolding in a supple and rich variety of hierarchically ordered beings, is the principal. We would therefore be inclined to believe the testimony of Philo of Alexandria (despite a contrary text from the doxographer Aetius), who says that Posidonius abandoned universal conflagration and supported the eternity of the world. 21
References
- Cicéron, Tusculanes, II, 26, 61 ; Pline, Histoire naturelle,, VII, 30 ; Plutarque, Vie de Pompée, 42 (cf. Arnim, Dio von Pniso. p. 93).
- Philon, De l’Incorruptibilité, II, p. 497, éd. Mangey ; Aetius, Placita, II, 9, 3. ‘
Source: Émile Bréhier(1951). Histoire de la philosophie, Presses Universitaires de France. Translation and adaptation by © 2025 Nicolae Sfetcu
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