The former is a negative definition, which shrinks with each new discovery. The latter is a positive definition, stronger with each new discovery. Certainly we may reach a point of diminishing returns, where we run out of variables to check. We aren't close yet.You argue that my saying "you cannot predict everything" is resorting to god-of-the-gaps, yet you have no problem making a similar assumption that even though we can't explain everything, someday we will. Should we call this "god-of-the-caulk"?
In physics, we used to have inner causes, too. Things fell to earth because they wanted to. Physics took off after we abandoned the inferred inner causes for the empirically testable external ones. There is still uncertainty here, too--just ask Heisenberg. But a very real limit to observation there does not suddenly offer proof that the inner cause is right. Negative definitions don't work that way. If we can find no more environmental causes for a behavior, you will say it is internally caused. Perhaps, though, it was caused by the gods. Or my psychokinetic cat. Or Iacchus's dream. Ah, but it has the appearance of free will? So do those.
