In his biography of Pythagoras in his Lives and Opinions of Eminent Philosophers, Diogenes Laërtius (3rd century CE) cites the statement of Aristoxenus (4th century BCE) that Themistoclea taught Pythagoras his moral doctrines: 
Aristoxenus says that Pythagoras got most of his moral doctrines from the Delphic priestess Themistoclea.
Porphyry (233 - 305 CE) calls her Aristoclea (Aristokleia), although there is little doubt that he is referring to the same person. Porphyry repeats the claim that she was the teacher of Pythagoras:
He (Pythagoras) taught much else, which he claimed to have learned from Aristoclea at Delphi.
The 10th-century Suda encyclopedia calls her Theoclea (Theokleia) and states that she was the sister of Pythagoras, but this information probably arises from a corruption and misunderstanding of the passage in Diogenes Laertius.
- Mary Ellen Waithe, Ancient women philosophers, 600 B.C.–500 A.D., p. 11
- Diogenes Laertius, Lives of Eminent Philosophers
- Gilles Ménage, (1984), The history of women philosophers, page 48. University Press of America. "The person who is referred to as Themistoclea in Laertius and Theoclea in Suidas, Porphyry calls Aristoclea."
- Porphyry, Life of Pythagoras, 41
- See Suda On Line, Pythagoras, π3124, and footnote 25: "This information suffers from a corruption in the text, arising from a misunderstanding of a source. Diogenes Laertius' passage actually reads, as the Suda does, Θεοκλείας ἀδελφῆς, but the whole remark is related to the legend of Pythagoras receiving his doctrine from a priestess in Delphi, whose name is Θεμιστόκλεια. Diogenes himself gives the correct information in a previous passage of the Life: cf. 8 παρὰ τῆς Θεμιστοκλείας τῆς ἐν Δελφοῖς."