Unless you can demonstrate that every single body of mass in the universe always obeys the inverse square law (and that's a lot of bodies), then Gravity remains a theory. The observation that a single apple accelerates toward the center of the Earth is a fact, but the generalization of that to the Law of Gravity is theory...as is the explanation for what gravity _is_ (folded spacetime or gravitons). Gravity is a theory _and_ a fact.

So is evolution.