Thrasyllus was a famous astrologer and scholar who flourished in the early first century CE. He is mainly known as the personal astrologer to the Roman Emperor Tiberius, although he also arranged the works of Plato and Democritus, and may have played an influential role in the history of philosophy due to these editorial efforts.
He became a legendary figure in subsequent centuries due to his friendship and interactions with Tiberius, and his views on certain astrological techniques and concepts continued to be cited by astrologers for several centuries after his death.
The Life and Dating of Thrasyllus
The Roman historians Tacitus, Seutonius and Cassius Dio indicate that Tiberius began consulting Thrasyllus during the former’s self-imposed exile on the island of Rhodes, which took place between 6 BCE and 2 CE. Based on this we know that Thrasyllus was already established as a practicing astrologer by the late 1st century BCE, and he began his role as astrologer to the future Emperor at least by the year 2 CE, when Tiberius left Rhodes.
The Roman historian Cassius Dio informs us that the Emperor Tiberius died the following spring after the death of Thrasyllus (Dio, Roman History, 58: 27). Since we know from other sources that Tiberius died in the year 37, this puts Thrasyllus’ death as having taken place in the year 36 CE.
Full Name and Place of Origin
At some point Thrasyllus attained Roman citizenship through the help of Tiberius. A Roman inscription records that his full name became Tiberius Claudius Thrasyllus (T8 in Tarrant).
There is some dispute amongst historians over his place of origin. A number of secondary sources over the past century have said that Thrasyllus originated in Alexandria, although none of the extant testimonia seem to explicitly make this connection.
There are some fragments on the study of stones attributed to a Thrasyllus of Mendes (T11 in Tarrant), which was a city in northern Egypt, although it is not clear if this Thrasyllus is the same as the astrologer-philosopher. As Tarrant points out (Thrasyllan Platonism, p. 7, fn. 11), Thrasyllus’ interests are known to have been wide enough that there isn’t necessarily any reason to think that he could not have been the author of a work on stones. If he was in the fact author of this work, then the astrologer’s name was originally Thrasyllus of Mendes, although he is referred to almost universally in later sources simply as Thrasyllus.
Father of Balbillus
The historian Tacitus says that Thrasyllus had a son who predicted Nero’s reign (Tacitus, The Annals, 6: 22), and some scholars have inferred that this son was probably the astrologer Balbillus, who served as court astrologer to the Emperors Claudius, Nero and Vespasian. This connection between Thrasyllus and Balbillius was first argued by Conrad Cichorius in 1922 (Römische Studien, pp. 390-398), and subsequently endorsed and explored by Frederick Cramer (Astrology in Roman Law, p. 95). Recently scholars such as Tarrant (Thrasyllan Platonism, p. 10) and Beck (The Mysteries of Mithras, p. 127, fn. 60) have taken a more cautious approach, choosing to suspend judgement on whether the two are related.
I tend to side with those who argue that Balbillus probably was Thrasyllus’ son, based on Tacitus’ statement that he plans to talk about the son later within the context of Nero in particular, and then the subsequent prominence of Balbillus during the reign of Nero. If we take this connection between the two for granted, then Thrasyllus may have been the central figure in a family line of prominent astrologers that stretched from the 1st century BCE through the mid 2nd century CE (Cramer, Astrology in Roman Law, p. 92ff).
Thrasyllus’ Astrological Work
Thrasyllus is known to have written an astrological text titled Table (Pinax), which was dedicated to an unknown figure named Hierocles. Unfortunately this work did not survive into the present time, although we do possess a summary of it that gives us some idea as to its contents.
Influence on the Astrological Tradition
Thrasyllus is mentioned once by the 2nd century astrologer Vettius Valens within the context of a method for rectifying the degree of the Ascendant (Valens, Anthology, 9, 11: 10). Valens says at the beginning of the chapter that the method was handed down by his predicessors, and then at the end of that chapter that Thrasyllus himself used the method. It seems likely that this brief chapter is simply a summary of a technique that Valens read in one of Thrasyllus’ works.
In the late 3rd century Porphyry cited Thrasyllus in chapter 24 of his Introduction to the Tetrabiblos for his views on the concept of “striking with a ray” (aktinobolia). This passage seems to have originally occurred within the context of a discussion about the length of life technique and the concept of “releasing” (aphesis), which is known in modern times as primary directions (see Gansten, Balbillus and the Method of aphesis).
Porphyry mentions Thrasyllus again in chapter 41 of his Introduction, grouping him together with Petosiris and other unnamed “elders” (πρεσβυτέρων) who advocated a system of bounds or terms (horia) that were different from the sets advocated by Ptolemy and Apollinarius. This seems to imply that Thrasyllus used the so-called Egyptian terms or bounds, which are usually thought to have been popularized by the writings attributed to Petosiris.
In the 5th century Hephaistio of Thebes mentioned Thrasyllus twice in his Apotelesmatika, citing him for the opinion that Aries and Libra are not capable of hearing or seeing each other (Apotelesmatika 2, 11: 57 and 2, 23: 13), despite the conventional doctrine that they can since they are both equinoxial signs.
These references seem to indicate that Thrasyllus’ astrological works had some circulation in the later tradition, at least through the 5th century. In some ways he seems to have been somewhat conventional, only citing Hermes, Nechepso and Petosiris in his treatise, and even being grouped together with Petosiris by Porphyry.
On the other hand, it seems that he was not entirely adverse to re-conceptualizing or sometimes even breaking with the tradition, for example in his treatment of hearing and seeing signs cited by Hephaistio, or perhaps even in his treatment of “striking with a ray” as cited by Porphyry. There Porphyry seems to contrast Thrasyllus’ view that striking with a ray can occur on either the right or left side of a planet with what may have been an earlier school of thought, where striking with a ray can only occur when a planet casts a ray towards a planet on its right side (earlier in zodiacal order).
The picture that these meager fragments of Thrasyllus’ work provide us is of someone who was both a preserver of the tradition as well as an occasional innovator.
Influence as a Philosopher
Aside from his work as an astrologer, Thrasyllus also has the reputation of being a semi-important figure in the history of philosophy. According to the 3rd century biographer Diogenes Laertius, Thrasyllus is responsible for arranging the works of Plato and Democritus into sets of four, otherwise known as tetralogies (Laertius, Lives, book 9: 45 and book 3: 56-61).
Harold Tarrant wrote a book exploring Thrasyllus’ role in arranging the Platonic corpus, in which he argued that Thrasyllus was an important figure in shaping the way that the texts have been read over the past 2,000 years, as well as as a significant philosopher in his own right (Tarrant, Thrasyllan Platonism).
In Porphyry’s Life of Plotinus he quotes a passage from his teacher Longinus where Thrasyllus is mentioned together with a group of philosophers who wrote on Pythagorean and Platonic philosophical principles (Porphyry, On the Life of Plotinus: 20). This essentially matches Tarrant’s assessment of Thrasyllus as a Platonist with Pythagorean leanings.
The Greek text of the summary of Thrasyllus’ Table was originally edited in the CCAG:
- Catalogus Codicum Astrologorum Graecorum, vol. 8, part 3, ed. Petrus Boudreaux, Lamertin, Brussels, 1912, pp. 99-101.
A complete collection of all known testimonia and fragments from Thrasyllus was published in an appendix to Harold Tarrant’s book on Thrasyllus’ influence on the philosophical tradition:
- Harold Tarrant, Thrasyllan Platonism, Cornell University Press, Ithaca, NY, 1993, pp. 215-249.
Note that the fragments and testimonia in Tarrant’s collection are left in Greek and Latin, untranslated.
- The Astrological Record of the Early Sages in Greek, trans. Robert Schmidt, ed. Robert Hand, The Golden Hind Press, Berkeley Springs, WV, 1995, pp. 57-60.
Schmidt published a revised translation of the same summary in 2009:
- Antiochus, with Porphyry, Rhetorius, Serapio, Thrasyllus, Antigonus et al., Definitions and Foundations, trans. and comm. Robert H. Schmidt, The Golden Hind Press, Cumberland, MD, 2009, pp. 341-345.
Beck, Roger. “The Mysteries of Mithras: A New Account of Their Genesis,” The Journal of Roman Studies, Vol. 88, 1998, pp. 115-128.
CCAG 8, 3 = Catalogus Codicum Astrologorum Graecorum, Vol. 8, Part 3, ed. Petrus Boudreaux, Lamertin, Brussels, 1912.
Cichorius, Conrad. Römische Studien. Teubner, Leipzig and Berlin, 1922.
Cichorius, Conrad. “Der Astrologe Ti. Claudius Balbillus, Sohn des Thrasyllus.” Rheinisches Museum für Philologie, 76, 1927, pp. 102–105.
Cramer, Frederick H. Astrology in Roman Law and Politics. American Philosophical Society, Philadelphia, PA, 1954.
Dio, Cassius. Roman History. Translated by Earnest Cary, 9 vols., Loeb Classical Library, Harvard University Press, Cambridge, MA, 1914-1927.
Gansten, Martin. “Balbillus and the Method of aphesis,” Greek, Roman, and Byzantine Studies 52, 2012, pp. 587–602. [PDF link]
Hephaistio of Thebes. “Apotelesmatika.” Edited in Hephaestionis Thebani apotelesmaticorum libri tres. 2 vols., ed. David Pingree, Teubner, Leipzig, 1973-4.
Krappe, Alexander Haggerty. “Tiberius and Thrasyllus.” The American Journal of Philology, Vol. 48, No. 4 (1927), pp. 359-366.
Laertius, Diogenes. Lives of Eminent Philosophers. 2 vols., trans. R. D. Hicks, Loeb Classical Library, Harvard University Press, Cambridge, MA, 1925.
Oliver, Revilo P. “Thrasyllus in Tacitus (Ann. 6.21).” Illinois Classical Studies 5, 1980, pp. 130-148. [PDF Link]
Porphyry, “Introduction to the Apotelesmatika of Ptolemy,” edited in Porphyrii Philosophi, Introductio in Tetrabiblum Ptolemaei, ed. Emilie Boer and Stephen Weinstock, in Catalogus Codicum Astrologorum Graecorum, vol. 5, part 4, ed. Stephen Weinstock, Royal Academy of Belgium, Brussels, 1940, pp. 187-228.
Porphyry, “On the Life of Plotinus,” translated in Neoplatonic Saints: The Lives of Plotinus and Proclus by Their Students, trans. Mark Edwards, Liverpool University Press, 2000.
Schmidt, Robert (trans.) and Robert Hand (ed.). The Astrological Record of the Early Sages in Greek, The Golden Hind Press, Berkeley Springs, WV, 1995.
Schmidt, Robert H. (trans. and comm.). Antiochus, with Porphyry, Rhetorius, Serapio, Thrasyllus, Antigonus et al., Definitions and Foundations. The Golden Hind Press, Cumberland, MD, 2009.
Tacitus. The Annals of Imperial Rome. Translated by Michael Grant, Penguin Books, London, 1956 (rev. ed. 1989).
Tarrant, Harold. Thrasyllan Platonism. Cornell University Press, Ithaca, NY, 1993.
Thrasyllus, “Summary of The Table,” edited in Catalogus Codicum Astrologorum Graecorum, Vol. 8, Part 3, ed. Petrus Boudreaux, Lamertin, Brussels, 1912, pp. 99-101.
Valens, Vettius, “Anthology.” edited in Vettii Valentis Anthologiarum Libri Novem. ed. David Pingree, Teubner, Leipzig, 1986.
- Author: Chris Brennan
- Originally published: March 8, 2012 | Last updated: March 27, 2014
- Article notes: The article is more or less complete, but could stand to be expanded in certain sections.
- Cite this article: Chris Brennan, “Thrasyllus,” The Hellenistic Astrology Website, March 27, 2014, https://www.hellenisticastrology.com/astrologers/thrasyllus/