Diogenes Laertius, Lives of the Eminent Philosophers 2.13: Simon

“Simon was an Athenian and a leather-worker. Socrates used to go to his workshop and talk to him and he wrote down everything he remembered. This is why people call his dialogues “leathered”. There are thirty of them in one book.

[list of dialogues]

People say that Simon was the first person to have dialogues in the Socratic fashion. When Pericles said he would fund him and asked him to join his side, Simon said “I would never sell my freedom of speech”. Another Simon composed speeches On Rhetoric; a second was a doctor around the time of Seleukos Nicanor; a third was a sculptor.”

Σίμων Ἀθηναῖος, σκυτοτόμος. οὗτος ἐρχομένου Σωκράτους ἐπὶ τὸ ἐργαστήριον καὶ διαλεγομένου τινά, ὧν ἐμνημόνευεν ὑποσημειώσεις ἐποιεῖτο· ὅθεν σκυτικοὺς αὐτοῦ τοὺς διαλόγους καλοῦσιν. εἰσὶ δὲ τρεῖς καὶ τριάκοντα ἐν ἑνὶ φερόμενοι βιβλίῳ·

Οὗτος, φασί, πρῶτος διελέχθη τοὺς λόγους τοὺς Σωκρατικούς. ἐπαγγειλαμένου δὲ Περικλέους θρέψειν αὐτὸν καὶ κελεύοντος ἀπιέναι πρὸς αὐτόν, οὐκ ἂν ἔφη τὴν παρρησίαν ἀποδόσθαι.

Γέγονε δὲ καὶ ἄλλος Σίμων ῥητορικὰς τέχνας γεγραφώς· καὶ ἕτερος ἰατρὸς κατὰ Σέλευκον τὸν Νικάνορα· καί τις ἀνδριαντοποιός.

From Michael Apostolios, Paroemiographer

“I know Simôn and Simôn knows me.” There were two leaders, Nikôn and Simôn. Simon overpowered him because he was a man of the worst ways and it is said that he erased all memory of Nikôn. This proverb is used for people who recognize the evil in one another.”

Οἶδα Σίμωνα καὶ Σίμων ἐμέ: δύο ἐγένοντο ἡγεμόνες, Νίκων καὶ Σίμων. ὑπερίσχυσε δὲ ὁ Σίμων κακοτροπώτατος ὢν, ὥστε καὶ τὴν ἐπὶ Νίκωνα φήμην ἀπαλεῖψαι. λεχθείη δ’ ἂν ἡ παροιμία ἐπὶ τῶν ἀλλήλους ἐπὶ κακίᾳ γινωσκόντων.

From the Suda,  tau 293

“Telkhines: evil gods. Or jealous and harmful humans. There were two Telkhines, Simôn and Nikôn. Nikôn overpowered and erase dthe memory of Simôn. So, there is the proverb, “I know Simon and Simon knows me. This is used for those who recognize evil in one another.”

Τελχῖνες: πονηροὶ δαίμονες. ἢ ἄνθρωποι φθονεροὶ καὶ βάσκανοι. δύο ἐγένοντο Τελχῖνες, Σίμων καὶ Νίκων. ὑπερίσχυσε δὲ ὁ Νίκων τὴν ἐπὶ Σίμωνι φήμην ἀπαλεῖψαι. καὶ παροιμία· οἶδα Σίμωνα καὶ Σίμων ἐμέ. ἐπὶ τῶν ἀλλήλους ἐπὶ κακίᾳ γινωσκόντων.

Zenobius explains it all

“I know Simôn and Simôn knows me”: There were two leaders who were evil Telkhinians by birth—for they were making the land infertile by spraying it with water from the Styx. They were Simôn and Nikôn. Simon overpowered because he was the most evil in his ways with the result that he erased any memory of Nikôn. For this reason in the proverb they only name Simôn. The proverb is applied to those who recognize the evil in one another.”

Οἶδα Σίμωνα καὶ Σίμων ἐμέ: Τελχίνων φύσει βασκάνων ὄντων, (καὶ γὰρ τῷ τῆς Στυγὸς ὕδατι τὴν  γῆν καταῤῥαίνοντες ἄγονον ἐποίουν,) δύο ἐγένοντο ἡγεμόνες, Σίμων καὶ Νίκων. ῾Υπερίσχυε δὲ ὁ Σίμων κακοτροπώτατος ὢν, ὥστε τὴν ἐπὶ Νίκωνι φήμην ἀπαλεῖψαι. Διόπερ οἱ παροιμιαζόμενοι μόνον τὸν Σίμωνα ὀνομάζουσι. Λεχθείη δ’ ἂν ἡ παροιμία ἐπὶ τῶν ἀλλήλους ἐπὶ κακίᾳ γινωσκόντων.

Sigma 447 [A completely different Simon]

“Simôn, Simonos: a proper name and also a proverb: “No one is more thieving than Simôn.” And Aristophanes adds that whenever [people] see Simôn, they immediately turn into wolves. He was a Sophist who took public property for his own. Simôn and Theoros and Kleonymos are perjurers. Aristophanes has, “if a thunderbolt hits perjurers, how did it not burn Simôn, or Kleônumos or Theôros?”

Σίμων, Σίμωνος: ὄνομα κύριον. καὶ παροιμία· Σίμωνος ἁρπακτικώτερος. ᾿Αριστοφάνης· ὅταν ἴδωσι Σίμωνα, λύκοι ἐξαίφνης γίνονται. σοφιστὴς δὲ ἦν, ὃς τῶν δημοσίων ἐνοσφίζετο. Σίμων καὶ Θέωρος καὶ Κλεώνυμος, οὗτοι ἐπίορκοι. ᾿Αριστοφάνης· εἴπερ βάλλει τοὺς ἐπιόρκους ὁ κεραυνός, πῶς δῆτ’ οὐχὶ Σίμων’ ἐνέπρησεν οὐδὲ Κλεώνυμον οὐδὲ Θέωρον; καί τοι σφόδρα γ’ εἰσὶν ἐπίορκοι.