Pl. Ap. 21e3-e6

[NateD26]

μετὰ ταῦτ᾽ οὖν ἤδη ἐφεξῆς ᾖα, αἰσθανόμενος μὲν [καὶ] λυπούμενος καὶ δεδιὼς ὅτι ἀπηχθανόμην,
ὅμως δὲ ἀναγκαῖον ἐδόκει εἶναι τὸ τοῦ θεοῦ περὶ πλείστου ποιεῖσθαι—ἰτέον οὖν, σκοποῦντι
τὸν χρησμὸν τί λέγει, ἐπὶ ἅπαντας τούς τι δοκοῦντας εἰδέναι.

In the first part of the sentence, the subject is Socrates, hence the participles are in nominative.
But In the second part, the impersonal verb ἐδόκει must have an implied μοι, because how else
could I explain why σκοποῦντι is in dative in the following parenthetical remark?

[modus.irrealis]

I would say the dative is due to the dative implied by ἰτέον.

[NateD26]

I would say the dative is due to the dative implied by ἰτέον.

What does it mean then?
"One/I must go, by examining well what the oracle means, to all those who think they know something" ?

[modus.irrealis]

Yes, except that it should be in the past tense, and I would also say just "examining" rather than "by examining". I also read δοκοῦντας here as meaning "are consider to be" or "appear" rather than "think".

[NateD26]

I think after reading your last comment about this actually being a past tense, i understand the sentence better, with
the reason for dative as well.
ἰτέον here is basically akin to ἀνάγκη μοι ἦν ἰέναι ἐπὶ χ, σκοποῦντι...

[modus.irrealis]

Exactly.