Ancient Greek Theory of Geocentrism

Alright, my brainy friends: it won’t take you but a New York minute to look at this diagram and figure out what’s wrong here.

That’s right! The earth is in the middle of the entire universe, and of course we know that’s just silly. But such was the model of the cosmos bequeathed by the Ancient Greeks that lasted from Aristotle through the Early Modern Period – about 1900 years! Also wrong here, but Aristotelian, are 1) the layers of “elements” arranged from heaviest to lightest (earth, water, air, fire), 2) the relative placement of the wandering bodies in the sky, and 3) a circle of stars encased in a crystalline sphere.

In fact, Aristotle & co (shout-out to Ptolemy here) had really good reasons to come up with this model — these scientists were able to predict with impressive accuracy the places where the planets and stars would be at any given time or year — no small feat! However, what is interesting to me is the way in which Aristotle’s philosophical beliefs profoundly shaped this vision.

And one of the most significant of these beliefs is his idea that the universe is teleological — that is, he thought that things existed *for a purpose*. And figuring out this purpose is one of the things Aristotle enjoyed writing about most. In Book XI of his _Metaphysics_, Aristotle articulates the idea that the stars move about in perfect circles around earth because of their desire to best imitate the initial causes of all movement – the prime movers, or gods. These gods, Aristotle thought, had no prior cause and were completely unchanging and perfect. The stars were closest to perfection because their relative positions never changed, but nevertheless were less perfect than the prime movers, because stars move, but the gods were not subject to change: they were the “unmoved movers”. Today, science asks non-teleological questions for the most part: “how does it happen?” can be addressed, whereas “why does it happen?” is always subject to interpretation.