A first, very introductory presentation of fragility as linked to both nonlinearity and dislike of variations. Antifragility is almost the opposite, limited to a specific range of variations.
Explains:
+ Why everything fragile must be concave.
+ The medical S curve.
+ Why harm to the climate is necessarily nonlinear in dose response.
+ How hospitals can be overcrowded unless there are redundancies.
Futher discussions will be more technical.