Herbert Weir Smyth, A Greek Grammar for Colleges

a. Not in Indirect Discourse.—Here verbs of perceiving denote physical perception—the act perceived or heard of. With ἀκούω and πυνθάνομαι the participle stands in the genitive; with αἰσθάνομαι it usually stands in the accusative (as with ὁρῶ), but sometimes in the genitive. (See 1361, 1367.)

““εἶδε Κλέαρχον διελαύνοντα” he saw Clearchus riding through” X. A. 1.5.12; ““αἰσθόμενος Λαμπροκλέα_ πρὸς τὴν μητέρα χαλεπαίνοντα” perceiving Lamprocles angry with his mother” X. M. 2.2.1, ᾔσθησαι πώποτέ μου ἢ ψευδομαρτυροῦντος ἢ συ_κοφαντοῦντος; have you ever noticed me either bearing false witness or playing the part of an informer? 4. 4. 11; ““ἤκουσαν αὐτοῦ φωνήσαντος” they heard him speaking” X. S. 3. 13; ““ὡς ἐπύθοντο τῆς Πύλου κατειλημμένης” when they learned of the capture of Pylos” T. 4.6.

N. Verbs of physical perception, ὁρῶ (especially) and ἀκούω, regularly take the present participle in Attic prose, which usually refuses to distinguish between I see a house burning and I see a house burn. The complexive aorist, summing up the action, does however occur, as ““ὡς εἶδεν ἐλαφον ἐκπηδήσα_σαν . . . ἐδίωκεν” when he saw a hind break cover he gave chase” X. C. 1.4.8. Cp. πεσόντα εἶδον Hdt. 9.22.

b. In Indirect Discourse.—Here verbs of perceiving denote intellectual perception—the fact that something is perceived or heard of. With ἀκούω and πυνθάνομαι the participle stands in the accusative (as with ὁρῶ, αἰσθάνομαι). Cp. 1363, 1365, 2144, 2145.

““ὁρῶμεν πάντα ἀληθῆ ὄντα ἃ λέγετε” we see that everything you say is true” X. A. 5.5.24, ““αἰσθάνομαι ταῦτα οὕτως ἔχοντα” I perceive that this is so” X. M. 3.5.5, ““ἤκουσε Κῦρον ἐν Κιλικίᾳ ὄντα” he heard that Cyrus was in Cilicia” X. A. 1.4.5, ““ὅταν κλύῃ τινὸς ἥξοντ᾽ Ὀρέστην” when she hears from any one that Orestes will return” S. El. 293, ““πυθόμενοι Ἀρταξέρξην τεθνηκότα” having learned that Artaxerxes was dead” T. 4.50.