"That is not what I said, and it's not what's true. Something composed of only predictable parts is predictable itself, because there's no place for unpredictability to enter in."

Sorry, I thought that's what you meant by "I suppose it's logically possible that there are high-level priorities that are neither formed out of nor controlled by lower-level ones."

How do you know that two predictable actions composed must equal another predictable action? There is no a-priori reason to believe that is true in every possible universe. I regard actions as just another aspect of objects, like their attributes. Logic won't tell you that red + blue = purple, and it won't tell you how the actions of atom X with combine with atom Y.