Trying to translate some pieces of Aristotle's Phys. VIII 1

Hello everybody. I'm using an essay on Aristotle that I'm writing as translation practice and there's a bit I just can't understand:

εἰ฀ δ' ฀ὄ฀ντα προϋπῆρχεν ἀ฀εὶ฀ κινήσεως μὴ฀ οὔ฀σης, ἄ฀λογον μὲ฀ν φαίνεται καὶ฀ α฀ὐτόθεν ἐ฀πιστήσασιν, οὐ฀ μὴ฀ν ἀ฀λλὰ฀ μᾶ฀λλον ἔ฀τι προάγουσι τοῦ฀το συμβαίνειν ἀ฀ναγκαῖ฀ον

It would seem irration even on the spot ἐ฀πιστήσασιν [to knoledgeful people? to sages?]* if on the other hand things always pre-existed without there being change, but it's necessary [ἀ฀ναγκαῖ฀ον with an implicit to be?] for this to happen not yet more proceding [???]

* None of the translations I have at hand seem to translate ἐπιστήσασιν. As you may notice I really do not understand how the last part of the sentence even stands together.

Can anyone help? Thanks!