In the process he debunks the myth, even the decree, that we can obtain a zero-risk world. Instead we must understand tradeoffs and choices. Decreasing risks of one event will increase the risks of others. For instance, portfolio diversification reduces risks of loss but increases the risk of not obtaining an unusually large return. A community that fosters economic growth to avoid unemployment creates or increases crime and accidents from congestion.
Antiperspirant decreases the risk of odor but increases the risk of allergic reactions.
Ross suggests that we make informed decisions. We should understand the tradeoffs, quantify and compare the risks of alternatives, make objective choices, and, ultimately, be responsible for those choices. Optimization requires that we avoid overreaction. We possess an optimistic bias that leads us to underrate risks to our own persons. We tend to overestimate risks of events that are disproportionately visible, such as catastrophes.