I read this book for a graduate seminar on Aristotle.
Topic of Metaphysics is Ousia=substance and being. What is the meaning of being? With respect to matter and form, it is primarily about form. Analytically both can be separate and distinct, but not in reality. One can analyze matter by potentiality and actuality. Matter can't answer the question of being without form. Some natural things are always a composite of matter and form, it is the answer to the question of what is ousia or being in nature. Matter by itself can't give us the answer to what a thing is.

Ousia=substance and being. Ousia= Being is the "this" spoken of in primary ousia. This is contrary to Plato. Categories vs. Metaphysics. We can talk of the "being" as quality as "not white." Being spoken of in many ways but only of one thing, i.e., "the focal being." Word being has flexibility. Other flexible words is essence. (the what it is to be). In Greek for Aristotle, a bed is not an Ousia because it is from techne=craft it can have an essence. Ousia is reserved for material things self manufactured in nature. All things are derived from a primary ousia.
This has to do with focal being, health is such a word. When we talk about different aspects of health, it is not a universal definition like Socrates looks for. Aristotle says you can't find it. Thus, the word "being" is just a word in a sense a focal point like the word health, i.e. healthy skin, healthy food, then there is health, for Socrates what is health. Aristotle says no, health is unity by analogy. Aristotle is OK with using examples. Math is not independent knowledge, it is dependent on things math is not a primary existence. Being is neither a universal nor a genus, (genus is animal in hierarchy). It is as though Aristotle wants to say that the primary meaning of being is the "this" the subject, i.e. Socrates not human all by itself, not animal all by itself.

Ousia= Being is the "this" spoken of in primary ousia. This is contrary to Plato. Categories vs. Metaphysics. "This" is ontologically primary. Ontological= the most general branch of metaphysics, concerned with the nature of being.

In the categories discussion, he doesn't talk about the distinction between matter and form, it comes later on in the Physics and then the Metaphysics. The "this" is ontologically primary in terms of what the "being" something, what something is. Why would it be wrong to say that primary ousia can't be primary from the standpoint of knowledge, it can't be the distinction between ontological and epistemological? Why would it be wrong to say that the "this" the perceptible encounter wouldn't be primary from the standpoint of knowledge? Because, whatever the categories are whatever the notions of say "horse" the "this" is a horse, the "this" is ontologically primary, but it can't be epistemologically primary because a "this" by itself is just a "this" the question "What is this" called a horse is to involve the categories of knowledge. Therefore, from a knowledge standpoint, secondary ousia, which is things like categories and context, they have primacy in knowledge. However, from the standpoint of "being" the perceptible "this" has primacy. This is just a technical way of distancing him from Plato. In the Metaphysics, the question of form is primary Ousia. Ousia =form in Metaphysics. In Metaphysics, the "this" is simply matter. Aristotle did not give up on Ousia as form. This matter and form is never separated for Aristotle, thus a composite of matter and form is in the Metaphysics. In realm of nature, form and matter can't be separated for Aristotle. If you only talk about matter, you have nothing definable. You never come across things without their form. God is only exception to form and matter together.

Ousia as form and essence. The essence of a thing is "what" it is, it gives us knowledge. Definition= essence. Bronze can't be essence of circle, the form is important, not the matter.
Can't use abstract math to explain a human. When it comes to knowledge, we must emphasize the ousia as form. It isn't that first you have material things, and then the mind adds form to it, whatever the particular thing is, it always was that form. Then when we learn about it, we actually just discover what the thing is. Therefore, it is a process of coming to understand the universal, the essence, but that was always there in the thing, it just needed to be done. So what he is emphasizing in the Metaphysics is the idea of ousia as form, as some kind of essence, but never separated from matter!

Ousia — 1. Grammatically basic. 2. Ousia As Ontologically basic, something that exists in its own right. The 1st example is how humans speak, the 2nd example is how things really are, both are both side of the same coin.

Principle of Noncontradiction
Arche= principle, beginning and rule. Aristotle thought that this was the firmest of all principles. It is impossible for the same thing to both belong and not to belong to the same thing at the same time to the same thing in the same respect. An important governing thought in Western philosophy. A thing is what it is, it can't be equal to its opposite. Aristotle thought reality was organized this way. It has to do with both knowledge and being. Aristotle states that if this principle is true then it is the firmest of all principles both for knowledge and reality. In the same respect, what does it mean? It shifts depending on circumstances. From standpoint of knowledge and reality principle of noncontradiction is stable. The three factors of the principle are: the same thing, in the same time, in the same respect, is what Aristotle is calling the principle of noncontradiction. In order for knowledge to be reliable, these factors are in play. Can't be going up and down a hill at the same time. 1 of 3 factors has changed, time. A "hill" is both up and down but meaningless unless you think in relation of motion. Aristotle believes when it comes to knowledge and reality the principle of noncontradiction is most basic and most fundamental and evident principle, because without it we can't communicate or think about things. Aristotle explains well how we lead our life by the principle a very pragmatic explanation. This is a principle we live by as humans thus, no one can deny it!
If you talk about change as a potentiality, you have a way of solving the puzzle. This actually serves as a slap at Renee Descartes in the future wondering if he is conscious or in a dream state. All philosophy stems from wonder and puzzlement. Aristotle makes distinction between worthy puzzles or useless ones.

Emphasis between primary and secondary being, Ousia.
For Aristotle Ousia or being is not just a thing, many ways being can be understood. Primary Ousia is things perceptible in nature. Secondary Ousia or being is sometimes being is how we understand things, i.e., big or small, etc, this is how we talk about things. He stretches the way Ousia in many ways. Matter can't be primary being like atomists, nor form alone like Platonists. However, when we analyze beings, we can use secondary being. Idea of "is" or "being" will shift depending on what you are talking about. The term "being" has plurality to it, depending on how we regard it (like using a hammer as a paperweight). Even though Metaphysics emphasizes form, it is "this form." Primary thing is the "this."

He wants to move away from Plato's idea that we can separate matter from form. A things essence is going to be the ultimate answer to the question of what is being. However, a things essence can't be separated from its statement of thing, it is almost as though that this essence is going to mean the definition of a thing, "what it is." Then in some respects, it has the characteristics of a secondary being. If you want to know what is the big deal about the perceptible "this," the primary ousia? Again, and again, the best way you can get a handle on that is he is critiquing Plato! He wants to move away from Plato's idea that it is possible to understand beings apart from the material world. Aristotle does make certain commitments; he makes certain commitments to the idea that the primary sense of being must be used in nature that are evident to us.

The Platonist in Aristotle says if the mind desires and is naturally inclined to pursue knowledge and he gives us a map how does it acquire knowledge. The Platonist in Aristotle says in the Metaphysics that if all there is, is matter and form then there is always an element of elusiveness in things because matter cannot fully deliver how we know things. When he gets to the question of the Divine, he does so because he believes that the natural desire of the mind can know that it will not have a final resting place with respect to just composite things. Especially since these composite things are always changing because nature is the realm of movement and change and the idea of form will at least give us access to how we can know changing things and actuality and potentiality. Changing things will always have this element of excess, beyond the minds capacity to grasp.

His talk of the Divine is the idea that there is something in reality that will satisfy the minds' desire for the ultimate stable resting point. If change were the last word, the mind could never come to rest. This is what Heraclitus argued for, Aristotle didn't like it. He wants to grasp the final. For him the Divine is satisfaction for the mind to grasp reality.
Uber Ousia. Aristotle here is talking about 2 senses of eternity.

1. Endless time.
2. Timelessness. 1st is never begins, never ends this is eternity or infinity. 2nd