“Antifragile” is about fragility and it’s converse, antifragility. In fragile systems the benefits are small and visible, and the the side effects are potentially severe and invisible.
Taleb illustrates the basics of fragile/antifragile with the example of package to be shipped. If you were to pack glasses in the box, even carefully, you would still know that the box would not respond well to disturbances like being dropped or mishandled. Glasses are fragile. If you were to pack a steel cube in the box, you would have no such problem. Drop it or whatever, the cube is “robust”, not changed by disturbances. However, imagine if there was an item you put in the box that was improved by disturbances, that was made stronger or more capable by being mishandled. That is the true opposite of fragile, or as Taleb refers to this property – antifragile.
A key point he makes is that in our rush to help, fix, or support system – in short, *do something*, we often make systems more fragile in the long run. One of his primary examples is medicine. In our efforts to make relatively small improvements to peoples lives through intervention, our health in the long run becomes more fragile, subject to the long term effects of drugs and therapies, and by the lifestyles that continue to enable.
His point is that you bet on the most tested system, and the most tested system we know of is Mother Nature and evolution. Anything we do needs to be judged against systems that had millions of years of stresses. This is not to say that modern medicine is a bad thing, because when it is helpful, it is *very* helpful, but when it it used for relatively minor improvements, the risks outweigh the rewards.