Professor Taleb’s concept of antifragility was introduced in part I to highlight its potential innovative applications in finance, in terms of portfolio construction as well as single asset analysis. Stock analysts for instance, scrutinise companies’ performance, strategies, managerial abilities etc. to make conclusions on their expected earnings and risks. They then compare their views to the market’s implied assumptions. But what about fragility and antifragility? How can one measure what the market thinks? Part II proposes a method to prove fragility or antifragility, from the market’s perspective. It shows as an example that the S&P 500 index is fragile, and explains why the 20% level on the VIX signals potential major market instabilities.