Aristotle has not yet earned an adherent in me. His proofs are often elaborate, obscure and pedantic; and he is often more concerned with refuting earlier philosophers than providing a thorough explanation of his own system. He reminds me of Hegel in that he is never more arrogant and assured of his correctness than when he is in fact wrong.
There are in fact two overarching examples of Aristotle's errors contained in this book. He believed that the earth was the center of the cosmos and he believed that matter was infinitely divisible. Interestingly enough, in both cases, there were other philosophies in Aristotle's day that got both right in contrast to him. He notes that the Pythagoreans believed the sun to be the center and the earth to be one of the stars. I'm assuming that when Aristotle says that the Pythagoreans held that the earth was one of the "stars" they meant "wandering" stars (Greek planeton). How the Pythagoreans came to this conclusion is an interesting question and one I would love to know the answer to. Aristotle attempts to prove that the earth is the center by appealing to a rather archaic and obscure belief in the hierarchy of the four elements, i.e. earth goes to the center, fire goes upward to the extremities and air and water are in the middle, the former goes upward and the latter downward. Also, Aristotle notes that philosophers like Plato believed in the limited division of matter, as did the Atomists. I don't recall now how Aristotle attempted to refute them. I can say that it most likely was elaborate, tedious and unconvincing.
The most interesting section was toward the back of the book in the work called On Generation and Corruption, where he discusses the mutability of the four elements. He discusses the different qualities of these (e.g. moistness/dryness, hotness/coldness etc) and how a change in the qualities allows one element to be transmuted into another. This section was rather interesting because it appears to be the philosophical basis for the practice of alchemy.
I am going to try to get through another work of Aristotle's before concluding my research of him. I'm not sure I'm going to be able to get through the Organon right now, but I will make the attempt. ( )