How Aristotle got it Wrong
On the importance of conceptual frameworks

by Edward Z. Yang

One of the persistent myths about Aristotelean physics—the physics that was proposed by the Ancient Greeks and held up until Newton and Galileo came along—is that Aristotle thought that “heavier objects fall more quickly than light objects”, the canonical example being that of a cannon ball and feather. Although some fraction of contemporary human society may indeed believe this “fact,” Aristotle had a far more subtle and well-thought out view on the matter. If you don’t believe me, an English translation of his original text (Part 8) adequately gives off this impression. Here is a relevant quote (emphasis mine):

We see the same weight or body moving faster than another for two reasons, either because there is a difference in what it moves through, as between water, air, and earth, or because, other things being equal, the moving body differs from the other owing to excess of weight or of lightness.

The “other things being equal” is a critical four words that are left out even of Roman accounts of the theory. See for example Roman philosopher Lucretius:

For whenever bodies fall through water and thin air, they quicken their descents in proportion to their weights...

While I do not mean to imply the Aristotle was correct or at all near a Newtonian conception of physics, Aristotle was cognizant of the fact that the shape of the falling object could affect its descent (“For a moving thing cleaves the medium either by its shape”) and in fact, the context of these quotes is not a treatise on how bodies move, but about how bodies move through a medium: in particular, Aristotle is attempting to argue how bodies might move in “the void.” But somehow, this statement got misinterpreted into a myth that the majority of Westerners believed up until the advent of Galilean physics. Where did all of these essential details go?

My belief is that Aristotle lacked the crucial conceptual framework—Newtonian physics—to fit these disparate facts together. Instead, Aristotle believed in the teleological principal, that all bodies had natural places which they natural moved toward, which failed to have any explanatory power for many instances of physical experience. What generalizations he were able to make were riddled with special cases and the need for careful thought, that made the ideas difficult to be communicated without losing something in the process. This is not to say the careful thinking is not necessary: even when we teach physics today, it is extremely easy to make the same mistakes that our historic predecessors made: the facts of the matter may all “be in Newton’s laws”, but it’s not necessarily obvious that this is the case!

But as you learn about the applications of a theory, about the places where it easily can go wrong, it is critical to remember that these thoughts and intuitions are to be hung on the grander tree of the unifying and adequate theory. Those who do not are forever doomed to juggling a confusing panoply of special cases and disjoint facts and cursed with the inability to concisely express their ideas. And though I have not the space to argue it here, I also claim that this applies for every other sort of discipline for which you must accumulate knowledge.

tl;dr — Facts without structure are facts easily forgotten.