ὁ δὲ ὅλος λόγος ἐστὶν τὸ ‘ἐν ἑαυτῷ ἐτάζον’ τοῦτο προσαγορεύεσθαι ἓν ὂν δίχα,
I do not understand this construction, on what does the infinitive depend?
I read it as: ὁ δὲ ὅλος λόγος ἐστὶν τὸ ‘ἐν ἑαυτῷ ἐτάζον’, τοῦτο προσαγορεύεται ἓν ὄν δίχα.
Given the infinitive, I think rather “The whole logos is that εν-αὑτῳ εταζον (“in itself” “examining”) is called this as being a single unit split apart.”
The surrounding context explains.
ὁ δὲ ὅλος λόγος ἐστὶν τὸ ‘ἐν ἑαυτῷ ἐτάζον’ τοῦτο προσαγορεύεσθαι ἓν, ὂν δίχα,
The whole phrase, this τὸ ‘ἐν ἑαυτῷ ἐτάζον’/which inspects in itself, is to be pronounced as one while being twofold.