Vlastos on Reasons and Causes

Why is x F?
εἶναί τι ἕκαστον τῶν εἰδῶν καὶ τούτων τἆλλα μεταλαμβάνοντα αὐτῶν τούτων τὴν ἐπωνυμίαν ἴσχειν (Phaedo, 102a10-b2)
Each of the Forms exists and other things acquired their name by having a share in them.

The 1st part of this statement (claiming the safe but uninformative αἰτία):
∀F∀x∃ϕ (Fx ↔ x participates ϕ)
ϕ: Form, x: individual, F: immanent character designated by adjective or abstract noun.

The 2nd part of this statement (claiming the clever αἰτία):
Instead of mentioning just one Form, ϕ, Socrates now refers us also to another, Γ, so related to ϕ, that whatever is “named after” Γ, will also be name after ϕ (103e-104b). X is F because it participates in Γ and Γ entails ϕ.

Phaedo 100b-102e

Isn't Simmias shorter than Phaedo and taller than Socrates "by a head"? Why does Plato insist that "a head" cannot serve as a proper explanation of the above phenomena?

Being Tough Enough?

Τί οὖν; νῦν οὐ πᾶν τοὐναντίον ἡμῖν φαίνεται ἐργαζομένη, ἡγεμονεύουσά τε ἐκείνων πάντων ἐξ ὧν φησί τις αὐτὴν εἶναι, καὶ ἐναντιουμένη ὀλίγου πάντα διὰ παντὸς τοῦ βίου καὶ δεσπόζουσα πάντας τρόπους, τὰ μὲν χαλεπώτερον κολάζουσα καὶ μετ’ ἀλγηδόνων, τά τε κατὰ τὴν γυμναστικὴν καὶ τὴν ἰατρικήν, τὰ δὲ πρᾳότερον, καὶ τὰ μὲν ἀπειλοῦσα, τὰ δὲ νουθετοῦσα, ταῖς ἐπιθυμίαις καὶ ὀργαῖς καὶ φόβοις ὡς ἄλλη οὖσα ἄλλῳ πράγματι διαλεγομένη; οἷόν που καὶ Ὅμηρος ἐν Ὀδυσσείᾳ πεποίηκεν, οὗ λέγει τὸν Ὀδυσσέα· στῆθος δὲ πλήξας κραδίην ἠνίπαπε μύθῳ· (Phaedo, 94c9-d7)