Aristotle's Physics: A Guided Study
Joe Sachs
Rutgers University Press, 2011

"Material is described as that which, by its own nature, inherently yearns for and stretches out toward form.... Form, in turn, does not mean shape or arrangement, but some definite way of being-at-work. This is evident in Book II of the Physics and is arrived at by argument principally in the Metaphysics, VIII.2. Every being consists of material and form, that is, of an inner striving spilling over into an outward activity. Potency and being-at-work are the ways of being of material and form." (SACHS 2011, p. 21) [PSA: cf. 192a20)

"What Aristotle said was that motion is the being-at-work-staying-itself of a potency, just as a potency. When an ongoing yearning and striving for form is not inner and latent, but present in the world just as itself, as a yearning and striving, there is motion. That is because, when motion is present, the potency of some material has the very same structure that form has, forming the being as something holding-on in just that particular motion. This does not mean that every motion is the unfolding of some being into its mature form; every such unfolding can fall short, overshoot, encounter some obstacle, or interact in some incidental way with some other being. It does mean that no motion of any kind would take place if it were not those potencies that emerge of their own accord from beings. Motion depends on the organization of beings into kinds, with inner natures that are always straining to spill into activity. Only this dynamic structure of being, with material straining toward form an dform staying at work upon material, makes room for motino that is not just an inexplicable from the way things are, but a necessary and intrinsic part of the way things are." (SACHS 2011, pp. 22-23)

"A fourth kind of cause, in most cases the most important one of all, is the final cause. It is often equated with purpose, but purpose is only one kind of final cause, and not the most general. A deliberate action of an intelligent being cannot be understood except in terms of its purpose, since only in achieving that purpose does the action become complete. The claim that final causes belong to non-human nature becomes ludicrous if it is thought that something must in some analogous way have purposes. What Aristotle in fact means is that every natural being is a whole, and every natural activity leads to or sustains that wholeness. His phrase for this kind of cause is "that for the sake of which" something does what it does or is what it is." (SACHS 2011, p. 24)

"Aristotle regards entelecheia as one of the ultimate terms of discourse, and not itself definable, but in Book IX of the Metaphysics (1047a30-31; 1050a21-23) he says that its meaning converges with that of energeia, and in IX.6 he explains energeia by means of examples and analogies. The genus of which motion is a species is being-at-work-staying-itself, of which the only other species is thinghood. The being-at-work-staying-itself of a potency, as material, is thinghood. The being-at-work-staying-itself of a potency as potency is motion. A thing, in the primary sense of the word, an independent thing, is a fusion of materials, which *is* as potency, with the being-at-work that is its form. To be at all, a thing must be at-work-staying-itself, breathing and assimilating food if it is an animal, taking in nourishment from the earth and air if it is a plant, circling and maintaining the equilibrium of its parts if it is the cosmos. But an animal must be born, must grow, must develop, must go seek food; a plant must sprout, put forth roots, form leaves and seeds; and displaced pieces of the cosmos must travel up and down. These motions are all potencies staying-themselves as potencies, not fused into the states of active completion toward which they are potencies. That is what Aristotle says motion is." (SACHS 2011, p. 79)

"The true first mover is his soul, the being-at-work of his body as a whole, which is responsible for any motion that originates in him. Like the first mover in any sequence, that source is motionless not in the sense of being inert, but by being fully at-work, in an activity that is the same and complete at every instant.... In Aristotle's physics, a cause, to be a cause, must surpass the effect, and the relation is not quantitative. Every cause is a being at work that is fully what it is. A motion too is a being-at-work, but what it is fully is inherently not whole, but is a potency *of* some being. There was a mild formulation of this as 201b32-33, when motion was called an incomplete being-at-work (ateles energeia), a phrase used often in Aristotle's works and explained as the complete being at work of something incomplete. Here (and nowhere else in his writings) Aristotle uses a deliberately self-contradictory formulation, calling motion an incomplete being complete (ateles enteles-echein), to emphasize that no motion can stand on its own as a source of anything, not even of itself." (SACHS 2011, p. 210)

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