Theon of Alexandria (/ˌθən, -ɒn/; Ancient Greek: Θέων ὁ Ἀλεξανδρεύς; c. AD 335 – c. 405) was a Greek[1] scholar and mathematician who lived in Alexandria, Egypt. He edited and arranged Euclid's Elements and wrote commentaries on works by Euclid and Ptolemy. His daughter Hypatia also won fame as a mathematician.


Little is known about the life of Theon. He made predictions and observations of solar and lunar eclipses in 364 which show he was active at that time, and he is said to have lived during the reign of Theodosius I (379–395).[2]

The Suda, a tenth-century Byzantine encyclopedia, calls Theon a "man of the Mouseion".[3] However, both the Library of Alexandria and the original Mouseion were destroyed in the first century BC and according to classical historian Edward J. Watts, Theon was probably the head of a school called the "Mouseion", which was named in emulation of the Hellenistic Mouseion that had once included the Library of Alexandria, but which had little other connection to it.[4] Theon's school was exclusive, highly prestigious, and doctrinally conservative.[4] Neither Theon nor his daughter Hypatia seems to have had any connections to the militant Iamblichean Neoplatonists who taught in the Serapeum of Alexandria and instead preferred Plotinian neoplatonism.[4]

Theon was the father of the mathematician Hypatia, who succeeded him as head of his school[5] Theon dedicated his commentary on the Almagest to a boy named Epiphanius, who may have been his son.[6] Also, in his commentary on the Almagest he states that his daughter Hypatia contributed to Book III of the Almagest stating "the edition having been prepared by the philosopher, my daughter Hypatia."[7]

A lunar crater, Theon Junior, now bears Theon's name.


Edited works

It is known that Theon edited the Elements of Euclid. He may also have edited some other works by Euclid and Ptolemy, although here the evidence is less certain. The editions ascribed to Theon are:


Of his commentaries, those which are extant are:

Original works

Among Theon's lost works, the Suda mentions On Signs and Observation of Birds and the Sound of Crows; On the Rising of the Dog[-Star]; and On the Inundation of the Nile.[3]

See also


  1. ^ a b c d John M. McMahon, "Theon of Alexandria" entry in Virginia Trimble, Thomas Williams, Katherine Bracher (2007), Biographical Encyclopedia of Astronomers, pages 1133-4. Springer
  2. ^ a b c d e f O'Connor, John J.; Robertson, Edmund F., "Theon of Alexandria", MacTutor History of Mathematics Archive, University of St Andrews
  3. ^ a b Suda
  4. ^ a b c Edward Jay Watts, (2008), City and School in Late Antique Athens and Alexandria, page 191-192. University of California Press
  5. ^ Edward Jay Watts, (2006), City and School in Late Antique Athens and Alexandria. "Hypatia and pagan philosophical culture in the later fourth century", pages 197–198. University of California Press
  6. ^ a b Smith, William; Dictionary of Greek and Roman Biography and Mythology, London (1873). "Theon"
  7. ^ Rome, Adolphe (1931–1943). Commentaires de Pappus et de Théon d'Alexandrie sur l'Almageste. Tome III. Italy: Vatican. p. 807.
  8. ^ Frank J. Swetz, (1994), Learning Activities from the History of Mathematics, page 18
  9. ^ T L Heath, (1921), A History of Greek Mathematics, Vol. 1, page 57. Oxford
  10. ^ Thomas Little Heath (1921). A history of Greek mathematics. Oxford, The Clarendon Press.
  11. ^ a b James Evans, (1998), The History and Practice of Ancient Astronomy, page 240 and footnote 35. Oxford University Press. ISBN 0-19-509539-1
  12. ^ a b Anne Tihon, "Theon of Alexandria and Ptolemy's Handy Tables" in Noel M. Swerdlow, (1999), Ancient Astronomy and Celestial Divination, page 359. MIT Press. ISBN 0262194228
  13. ^ a b Alan Cameron, Jacqueline Long, (1993), Barbarians and Politics at the Court of Arcadius, page 45. University of California Press. ISBN 0520065506
  14. ^ A. Mark Smith, (1999), Ptolemy and the Foundations of Ancient Mathematical Optics, page 16. American Philosophical Society. ISBN 0871698935
  15. ^ a b James Evans, (1998), The History and Practice of Ancient Astronomy, page 276. Oxford University Press. ISBN 0-19-509539-1
  16. ^ James Evans, (1998), The History and Practice of Ancient Astronomy, page 156. Oxford University Press. ISBN 0-19-509539-1
  17. ^ a b James Evans, (1998), The History and Practice of Ancient Astronomy, page 90. Oxford University Press. ISBN 0-19-509539-1

Further reading