[nologic01]

ex-post an extraordinary event a lot of people are wise and can "rationalise" how it did happen.

the question is whether one can rationalize what can happen before it does.

that requires understanding in depth what the system is and how it might behave in extremes

open any quantitative finance book older than a few years and it will tell you that interest rates cannot go negative because... blah blah... some cash arbitrage

it turns out that arbitrage is not implementable...