The gravity model is similar though: we posit a force that pulls things together, but we don't know /why/ that force seems to exist, no more than the ancients knew /why/ the planets seemed to move in smaller circles along their circular paths. We're really not /that/ enlightened, after all.
I think that's right, but ultimately all explanations we have are based on prior knowledge that is itself not necessarily complete. It's explanations all the way down, until we hit some primary observations or axiomatic assumptions that are the hardest to get rid of.
"Enlightened" was my bad choice of a word. I get overexcited when I think of how much we have learned in the past couple thousand years and I forget that we mainly learned how little we know. Or can explain!
I'd like to think explaining means giving a model simpler than the observations. But this also can be true of a purely predictive model, that offers no "why". Another commenter pointed out that epicycles do simplify - so they do "explain" in this sense.
What defines an "explanation"? What makes something a "why"?
