Taleb uses ancient examples to explain the triad of Fragile, Robust, and Antifragile. Damocles, who dines with a sword dangling over his head, is fragile. A small stress to the string holding the sword will kill him.

The Phoenix, which dies and is reborn from its ashes, is robust. It always returns to the same state when suffering a massive stressor.

But the Hydra demonstrates Antifragility. When one head is cut off, two grow back.