The "bounce" is when you try to analyze a word like could, or a notion like possibility, and end up saying, "The set of realizable worlds [A'] that follows from an initial starting world A operated on by a set of physical laws f." Where realizable contains the full mystery of "possible" - but you've made it into a basic symbol, and added some other symbols: the illusion of formality.

Can you keep on "reducing" -- unpacking the meanings of terms -- without hitting a bedrock? Is there anyone who doesn't know what "can" and could" mean? Can you not co-define a set of words in terms of each other, coherentisically, without prejuice as to what is fundamental?