It is probably no understatement to say that Aristotle is out of favour with the contemporary scientific community, and it is not uncommon that mentioning his name at a scholarly workshop or conference ignites a general burst of laughter from the audience. This attitude is not limited to the fairly sheltered environment of a lecture-room, but can also be found in the popular scientific literature. S. Hawking and L. Mlodinow recently wrote in a popular book:
Aristotle, however, did not see problems in measurement and calculation as impediments to developing a physics that could produce quantitative predictions. Rather, he saw no need to make them. Instead, Aristotle built his physics upon principles that appealed to him intellectually. He suppressed facts he found unappealing and focused his efforts on the reasons things happen, with relatively little energy invested in detailing exactly what was happening. Aristotle did adjust his conclusions when their blatant disagreement with observation could not be ignored. But those adjustments were often ad hoc explanations that did little more than paste over the contradiction. In that manner, no matter how severely his theory deviated from actuality, he could always alter it just enough to seem to remove the conflict. (S. Hawking and L. Mlodinow, 2010, 24).
Hawking and Mlodinow don’t mince words and let us know, on the same page, that:
For example, his theory of motion specified that heavy bodies fall with a constant speed that is proportional to their weight. To explain the fact that objects clearly pick up speed as they fall, he invented a new principle-that bodies proceed more jubilantly, and hence accelerate, when they come closer to their natural place of rest, a principle that today seems a more apt description of certain people than of inanimate objects.
This is a travesty of Aristotle’s physics, and it illustrates the contemporary physicists’ disregard for Aristotle and his craft. And that is a shame, because his physics is actually quite entertaining and fun. And, as I want to show in this website, as long as you don’t confuse his physics with ours, he is not as daft as he is often depicted. First of all I show here that within his system Aristotle might very well have been right when he said that heavier things fall faster, ceteris paribus, than lighter ones. In a follow-up article I want to discuss a fundamental problem with our view of Aristotle’s local motion. When we are confronted with local motion in Aristotle’s physics we inevitably think of local motion as we know it, i.e. of concrete things moving through empty space while pushing other things out of their way. But that cannot be what Aristotle meant. Aristotle held that the world consisted of a plenum, and in his plenum local motion as we know it is impossible, so he must have had a different concept of local motion than we have. I shall show that there is a plausible, albeit rather peculiar, solution for this conundrum, that is consistent with Aristotle’s physics, even though he does not explicitly specify it.
This website is about what I make of Aristotle’s physics, and it is not intended to be some kind of textbook on Aristotle’s physics. And I am no Aristotle scholar (or any other kind of scholar for that matter), just somebody with an interest in unusual things and a lot of free time. But I do want to get the facts right, so please let me know if you find anything amiss.