1.) Nature is any principle of motion (cf. axiom #2) and is two sets of principles. The first set of principles is the term of becoming and its negation, the second a principle tending to being and not negation which Aristotle calls the underlying or matter.
2.) Matter can be considered as indifferent to diverse outcomes, e.g. flour can become bread, cake, or paste; and nitrogen and hydrogen might make ammonia, and we might take the ammonia and make hydrogen and nitrogen again. Though matter is indifferent to consider it as indifferent is not to consider it as a principle of nature, since nature is a principle of motion and no subject moves qua indifferent. Thus matter is (a) inherently a tendency to perfection and away from defect or privation and (b) this goodness is inherently manifold or realizable in ways that exclude each other. Aristotle is not just speaking metaphorically in saying that form is divine, for matter tends to form precisely as a good not limited to this or that good. While matter must be realized as this good A and not that good B, matter doesn’t tend to good A qua excluding good B. The good that matter tends to is therefore in a certain sense infinite and divine, matter tends to good and not as this finite good in opposition to that one. Failure to recognize the divine character of this good is one reason why we fail to see that nature is tending to a good: if, after all, nitrogen and hydrogen make ammonia as easily as ammonia makes nitrogen and hydrogen, what is the point of saying that either process is for a good and away from an evil? Which is the privation and which is the perfection? But this conflates the good to which matter tends with the finite goods considered precisely in their finitude or opposition to one another.
3.) Aristotle is solving the riddle of Parmenides and not side-stepping it. Aristotle does not shift the terms of motion from being as such to this or that being – that would be to side-step Parmenides – rather he puts a tendency to being as such in matter, and explains how matter is in one way being and in another way not even according to Parmenides’s own account of being. Matter is other than privation but it is also other than the intelligible in itself as it is only intelligible by analogy or comparison to another. Parmenides’s account of being therefore conflates the intelligible or true secundum quid with anything not intelligible or true simpliciter. Matter is not intelligible in itself or good in itself and so is not being in itself, but it is the intrinsic tendency to good and intelligibility and repugnance to non-being, unintelligibility, and evil.
4.) Aristotle closes book 1 by noting that it would take another discourse to get clear on just what sense matter seeks being as such. The discourse was what we call metaphysics but which Aristotle described better as divine science or theology. Just how much being does matter seek? How close to the divine is it trying to get? These are questions that Christianity will build on top of Aristotle: in what sense does matter seek even matter as it would have been in Aristotle’s heavenly bodies or in our light or resurrected body? Is matter inherently a tendency for union with immateriality (i.e. for the human person?) This was Dekoninck’s thesis, so much so that he said one can infallibly predict from the first moment of cosmic inflation that man must necessarily arise. Questions about the Blessed Mother are also hard to avoid, as we see in her a tendency of matter even toward a divine person, though of course not a tendency simpliciter but so far as matter is hypostatically united to a divine person.