Ah, I was only thinking of Plato's theory of forms, not Aristotle's, but it makes sense it would be more about something taking on a form in Aristotle, since he was much more concerned with biology than Plato, whose forms are more timeless.

Thanks for the Parmenides poem. It seems much more straightforward than the various commentaries and analyses I've seen written about it.

VIII.16: ἔστιν ἢ οὐκ ἔστιν· :: It is or it is not

Very nearly "to be or not to be"...