This commentary on Aristotle's Metaphysics comes down under the name of Alexander of Aphrodisias, the Peripatetic who held a public chair of Aristotelian philosophy under Septimius Severus and Caracalla, around 200 CE. Only the part on the first five books, Alpha to Delta, is his. The commentary on Epsilon to Nu, headed as scholia, is a later work transmitted with it; its author is most probably Michael of Ephesus, a Byzantine commentator of the twelfth century.
Alexander's part is a close exegesis. It quotes or paraphrases Aristotle section by section, explains the argument and Aristotle's review of earlier thinkers, notes variant readings, and asks how the books fit together: it judges Alpha Minor to be Aristotle's but only part of a book, and defends Delta, the catalogue of terms said in many ways, as belonging to the treatise. The later commentary follows the same plan more briefly, through Zeta and Eta on ousia and definition, Theta on dynamis and energeia, Iota on unity and Kappa, where it stops at chance and refers the reader to the Physics. It goes on to Lambda on the unmoved principle and nous, and ends with Mu and Nu on mathematical objects, the Ideas and ideal numbers. The commentary on Beta follows that on Alpha Minor under a single heading. The text survives in medieval manuscripts.
Alexander of Aphrodisias On Aristotle's Metaphysics, Commentary: summary and contents (PDF)
Alexander of Aphrodisias On Aristotle's Metaphysics, Commentary: summary and contents (Markdown)
Contents
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Α Book Alpha
Alexander begins with Aristotle's opening sentence, Pantes anthrōpoi tou eidenai oregontai physei, explaining knowledge as the perfection of the psychē and sight as the sense that shows most differences in things. He follows Aristotle's review of earlier thinkers on the causes, asking whether Empedocles' Love and Strife are one principle or two and what Anaxagoras meant, and ends by noting that the puzzles promised here are taken up in Beta and in Alpha Minor.
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Ἔλαττον Α καὶ Β Books Alpha Minor and Beta
Two books of the Metaphysics are covered under the title of Alpha Minor. The commentary first judges that short book to be Aristotle's but only part of a book, and asks where it belongs, since it argues that causes do not run to infinity yet ends like a preface to physics. It then passes to the puzzles of Beta, among them whether the axioms of demonstration belong to the philosopher and whether the principles are universal or particular.
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Γ Book Gamma
The study Aristotle calls wisdom, first philosophy and theology is here defined as the study of to on hēi on. Most of the commentary on Gamma follows the defence of the principle of non-contradiction: if contradictories were true together, everything would be one and everything said of a thing would hold only incidentally. It ends on the claim that neither everything rests nor everything moves, with a reminder of the unmoved mover shown in the Physics.
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Δ Book Delta
Aristotle's catalogue of terms said in many ways is shown at the outset to be genuine and to belong to the Metaphysics, since the philosopher studies what all the sciences share. Alexander works through the entries in turn, among them dynamis, including the capacity to be acted on for better or worse and how privation counts as a kind of having, and ends with to symbebēkos, referring the reader to the Posterior Analytics.
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Ε Book Epsilon
Headed scholia, like the commentary on the later books, the short commentary on Epsilon begins from the claim that the study of to on hēi on is the one that knows how each thing should be defined, unlike astronomy, which studies only the stars' motions. It explains the sophists' puzzles about cultured Socrates and literate Socrates, and about Aristarchus the grammarian, as arguments built on to kata symbebēkos on, which it sets aside together with what is in the sense of what is true.
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Ζ Book Zeta
Zeta and the book after it deal with definition, and the commentary opens by explaining why Aristotle starts from the many senses of to on: definitions belong properly to ousia and only in a qualified way to its attributes. It follows the question whether the definition of a whole contains its parts, argued through the circle and its segments and the syllable and its letters, and closes on form as the cause that makes the matter into flesh or into a syllable.
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Η Book Eta
Opening with the summary that begins Eta, which gathers the main points of the two books before it, the commentary sorts the causes of ousiai into forms, efficient and final principles, and matter. It discusses the followers of Antisthenes, who held that one can say what silver is like, namely tin, but cannot define it. At the end the commentator praises Aristotle's teaching, which leads the reader from how matter and form are one up to God, father and maker of all.
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Θ Book Theta
Having treated ousia in Zeta and Eta, Aristotle turns to dynamis and energeia, and the commentator explains why: the first aition is shown to be nothing but energeia. The commentary distinguishes what is named from its matter from what is named from its affections, so that a statue is called bronze but bronze is not called a statue. It ends with truth about unchanging things, where one cannot think the number two now prime and now not.
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Ι Book Iota
Unity is the subject. The commentary opens with the Platonists who made the One itself an ousia, sending the reader to Plato's Parmenides, and asks whether any such One exists after dividing the senses of one. It takes up sameness, likeness and difference, with two bronze statues the same but a bronze and a gold statue alike, and ends on how the one and the many are opposed, since the unit is a measure and so a relative term.
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Κ Book Kappa
Kappa, which the commentator counts the tenth book of the treatise, restates what was proved earlier and argues that this inquiry differs from physics and mathematics and alone deserves the name of wisdom. It goes over the arguments against those who hold that contradictories are true together, and then treats to kata symbebēkos on and its indeterminate causes. The commentary stops at the account of chance, sending the reader to the commentaries on the Physics, since the rest of Kappa repeats that work.
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Λ Book Lambda
Lambda concerns the first, unmoved principle for whose sake the whole treatise was written. The commentary begins with the senses of principle, matter, form and privation, and shows in what way all things have the same principles. It follows Aristotle to nous in act as the best of things and the final cause among the unmoved, citing his book On the Good, and ends with the Homeric line against the rule of many, which the commentator extends to one principle and one god.
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Μ Book Mu
Mu and Nu examine the Pythagorean and Platonic views of the principles. After recalling Lambda's first nous and the movers of the spheres, the commentary sets out three questions, whether mathematical objects exist, whether the Ideas and ideal numbers exist, and whether they are principles, and assigns the first two to Mu. It argues that ideal units, bodiless and without parts, cannot touch or mix to make a two, and ends on knowledge as of the universal dynamei and of the particular energeiai.
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Ν Book Nu
In Nu, the last book of the Metaphysics, Aristotle argues that neither ideal numbers nor mathematical objects can be the principles of things. The commentary meets those who admit only mathematical ousia with the objection that the world would then be episodic, since magnitudes, psychē and bodies would exist without numbers. It brings the whole commentary to its end, mentioning Aristotle's two books on the Forms, written outside the Metaphysics.