Subjects covered in this, the third and last, volume of translation of this work include: why the elements are four in number; what's wrong with Empedocles' theory of elements; how homogeneous stuffs, particularly the tissues of a living body, come to be and consist of the elements. The volume also contains very important discussions of causes, particularly of efficient cause, and of necessity in the sphere of generation and corruption. It will be of interest to the students of ancient philosophy and science (the commentary draws on earlier philosophical and medical texts); of Patristics and Christian Theology (it allows comparison of Philoponus' later creationist doctrine with his earlier ideas about generation); of medieval philosophy (this text was known to the Arabs; it is used by Avicenna and Averroes); and to anyone with interest in the metaphysics of causation, emergence, necessity and determinism.
Aristotle believed that the outermost stars are carried round us on a transparent sphere. There are directions in the universe and a preferred direction of rotation. The sun, moon and planets are carried on different revolving spheres. The spheres and celestial bodies are composed of an everlasting fifth element, which has none of the ordinary contrary properties like heat and cold which could destroy it, but only the facility for uniform rotation. But this creates problems as to how the heavenly bodies create light, and, in the case of the sun, heat. The topics covered in this part of Simplicius' commentary are: the speeds and distances of the stars; that the stars are spherical; why the sun and moon have fewer motions than the other five planets; why the sphere of the fixed stars contains so many stars whereas the other heavenly spheres contain no more than one (Simplicius has a long excursus on planetary theory in his commentary on this chapter); discussion of people's views on the position, motion or rest, shape, and size of the earth; that the earth is a relatively small sphere at rest in the centre of the cosmos.
In this, the first half of Philoponus' analysis of book one of "Aristotle's Physics", the principal themes are metaphysical. Aristotle's opening chapter in the "Physics" is an abstract reflection on methodology for the investigation of nature, 'physics'. Aristotle suggests that one must proceed from things that are familiar but vague, and derive more precise but less obvious principles to constitute genuine knowledge. His controversial claim that this is to progress from the universal to the more particular occasions extensive apologetic exegesis, typical of Philoponus' meticulous and somewhat pedantic method. Philoponus explains away the apparent conflict between the 'didactic method' (unavoidable in physics) and the strict demonstrative method described in the "Analytics". After 20 pages on chapter 1, Philoponus devotes the remaining 66 pages to Aristotle's objections to two major Presocratic thinkers, Parmenides and Melissus. Aristotle included these thinkers as an aside, because they were not engaged in physics, but in questioning the very basis of physics. Philoponus investigates Aristotle's claims about the relation between a science and its axioms, explores alternative ways of formalising Aristotle's refutation of Eleatic monism and provides a sustained critique of Aristotle's analysis of the Eleatics' purported mistakes about unity and being.