Act and potency are really distinct but not correlative, even in material being. Even where potency is intrinsic to essence, we cannot say that act depends on potency. We usually slip into thinking of act and potency as correlatives through an analogy to accidental forms and artifacts: a shape-in-the-clay clearly depends on clay; without fabric, the quilt pattern is a pure abstraction.
But this is not an insight into act but a feature of accidents. While it is possible to say, as Feser does, that a substantial form is an abstraction apart from its matter, this is only so far as act and potency are taken precisely as a potency that participates in the esse of the substance itself. This esse is logically prior to everything else: as Barry Miller proves in more or less all of his books, the existence-of-Socrates is logically prior to Socrates.
If we do not see act as logically prior to all potency then either the two are strict correlatives or possibility is logically prior to act. The correlative option is only believed by lazy AT theorists – and then only thoughtlessly – and so can be safely ignored. To articulate the position with any clarity would require seeing acts as sorts of potencies and potencies as sorts of acts. Taking matter as logically prior to act is the foundation of all materialism, mechanism, the Analytic doctrine of “possible worlds”, and most other forms of primitive thought. Potency is seen as the womb of being, as both the solid core of reality to which all things reduce (or from which all things ephemerally ;8″emerge” or “are actualized”) and the term of reduction that we can only reach after most of reality has been boiled off. All there is is a nebulous, flowing, power-and-stuff. The divine fertility of non-being.
But it would make more sense to take the tree as a projection of its shadow, which is not at all a bad way to understand the various attempts to understand the world of experience as having no logos except the metrical-mathematical (i.e. “scientific™“). There is, of course, nothing in the tree that is not in the shadow except subjective “secondary qualities”; it is much easier to measure a shadow of any length than a forty-foot tree; the shadows form a unified, purely quantitative forest of idealized, homogeneous mathematical extension; and, most importantly, there is nothing about the motion of the tree that cannot be predicted from the laws we discover in its shadow! God has written the book of the forest in the mathematical features of shadows! In fact, why believe in God at all when the laws we discover suffice to explain everything?
Ontologically, the material world does not reduce to the material or emerge from it. The material is a projection and participation of actuality. Matter projects from form and participated in it; matter and form as essence projects from and is sustained by esse; angelic essence does so from its angelic esse; and all potency whatsoever comes forth from pure act in a way that, while real, is not an addition to his being any more than the shadow adds mass.