He wrote extensively on eastern cultures, and is thought to have traveled to the Bactrian city of Ai-Khanoum (Alexandria on the Oxus) in modern Afghanistan.
Clearchus wrote extensively around 320BCE on Oriental cultures, from Israel to Persia to India, and several fragments from him are known. His book "Of Education" (Greek: Περὶ παιδείας, Peri paideiās) was cited by Diogenes Laërtius.
Clearchus in particular expressed several theories on the connection between western and eastern religions. In "Of Education", he wrote that "the gymnosophists are descendants of the Magi".
In another text, Josephus the first-century Romano-Jewish scholar claimed that Clearchus has reported a dialogue with Aristotle, where the philosopher states that the Hebrews were descendants of the Indian philosophers:
Jews are derived from the Indian philosophers; they are named by the Indians Calami, and by the Syrians Judaei, and took their name from the country they inhabit, which is called Judea; but for the name of their city, it is a very awkward one, for they call it Jerusalem.
Περὶ τῶν ἐνύδρων (Peri tōn enudrōn); on water-animals
Περὶ ϑινῶν (Peri thīnōn); on sand-wastes
Περὶ σκελετῶν (Peri skeletōn); an anatomical work
Περὶ ὕπνου (Peri upnou); on sleep (genuineness questionable)
There is some question as to whether the work on military tactics cited by Aelianus Tacticus should be ascribed to Clearchus of Soli or Clearchus of Heraclea.
In the Bactrian city of Ai-Khanoum, near the border with India, Greek verses, brought to city by Clearchus from Delphi, were dedicated to the founder of the city named Kineas. On a Herôon (funerary monument), identified in Greek as the tomb of Kineas (also described as the oikistes (founder) of the Greek settlement) and dated to 300-250 BC, the inscription says:[3]
As children, learn good manners.
As young men, learn to control the passions.
In middle age, be just.
In old age, give good advice.
Then die, without regret.
—(Ai Khanoum inscription)
The precepts were placed by a Greek named Clearchus, thought to be Clearchus of Soli, who had copied them from Delphi:
Whence Klearchos, having copied them carefully, set them up, shining from afar, in the sanctuary of Kineas
Excerpt of Chapter I-22, Josephus, Contra Apionem:
"For Clearchus, who was the scholar of Aristotle, and inferior to no one of the Peripatetics whomsoever, in his first book concerning sleep, says that "Aristotle his master related what follows of a Jew," and sets down Aristotle's own discourse with him. The account is this, as written down by him:
"Now, for a great part of what this Jew said, it would be too long to recite it; but what includes in it both wonder and philosophy it may not be amiss to discourse of. Now, that I may be plain with thee, Hyperochides, I shall herein seem to thee to relate wonders, and what will resemble dreams themselves. Hereupon Hyperochides answered modestly, and said, For that very reason it is that all of us are very desirous of hearing what thou art going to say. Then replied Aristotle, for this cause it will be the best way to imitate that rule of the Rhetoricians, which requires us first to give an account of the man, and of what nation he was, that so we may not contradict our master's directions. Then said Hyperochides, Go on, if it so pleases thee. This man then, [answered Aristotle,] was by birth a Jew, and came from Celesyria; these Jews are derived from the Indian philosophers; they are named by the Indians Calami, and by the Syrians Judaei, and took their name from the country they inhabit, which is called Judea; but for the name of their city, it is a very awkward one, for they call it Jerusalem. Now this man, when he was hospitably treated by a great many, came down from the upper country to the places near the sea, and became a Grecian, not only in his language, but in his soul also; insomuch that when we ourselves happened to be in Asia about the same places whither he came, he conversed with us, and with other philosophical persons, and made a trial of our skill in philosophy; and as he had lived with many learned men, he communicated to us more information than he received from us."
This is Aristotle's account of the matter, as given us by Clearchus; which Aristotle discoursed also particularly of the great and wonderful fortitude of this Jew in his diet, and
continent way of living, as those that please may learn more about him from Clearchus's book itself; for I avoid setting down any more than is sufficient for my purpose." Josephus, Contra Apionem, I