[Emphere]

Yep. What you're getting at in a sense is "Knightian uncertainty", the presence of unknown unknowns (aka "black swans"). And the heart of the matter is certainty, which we cannot hope to achieve. So what exactly do these tools for handling risk help us achieve? I think this is still a question of active investigation and at any rate, if good answers do exist for it, they certainly haven't filtered down to the common masses.