Ian Mueller - Böcker

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 value of Simplicius' commentary on "On the Heavens 2,1-9" lies partly in its preserving the lost comments of Alexander and in Simplicius' controversy with him. The two of them discuss not only the problem mentioned, but also whether soul and nature move the spheres as two distinct forces or as one. Alexander appears to have simplified Aristotle's system of 55 spheres down to seven, and some hints may be gleaned as to whether, simplifying further, he thinks there are seven ultimate movers, or only one.

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.

Commenting on the end of Aristotle "On the Heavens" Book 3, Simplicius examines Aristotle's criticisms of Plato's theory of elemental chemistry in the "Timaeus". Plato makes the characteristics of the four elements depend on the shapes of component corpuscles and ultimately on the arrangement of the triangles which compose them. Simplicius preserves and criticizes the contributions made to the debate in lost works by two other major commentators, Alexander the Aristotelian, and Proclus the Platonist. In Book 4, Simplicius identifies fifteen objections by Aristotle to Plato's views on weight in the four elements. He finishes Book 4 by elaborating Aristotle's criticisms of Democritus' theory of weight in the atoms, including Democritus' suggestions about the influence of atomic shape on certain atomic motions.

In the chapters of his 'Physics' commented on here, Aristotle disagrees with Pre-Socratic philosophers about the basic principles that explain natural changes. But he finds some agreement among them that at least two contrary properties must be involved, for example hot and cold. His own view is that there are two contrary principles at a more abstract level: the form possessed at the end of a change and the privation of that form at the beginning. But there is also a third principle needed to supply continuity - the matter to which first privation and later form belong. Despite the apparent disagreements, Simplicius, the Neoplatonist commentator, wants to emphasise the harmony of all pagan Greek thinkers, as opposed to Christians, on such a basic matter as first principles. He therefore presents not only the Pre-Socratics and Aristotle, but also himself and earlier commentators of different schools as all in basic agreement.