Bruce Jacobs sifts through the history of modern finance, from the efficient market hypothesis to behavioral psychology and chaos theory, to determine the cause of recent market crashes. He finds that some investment strategies, especially those based on theories that ignore the human element, can self-destruct, taking markets down with them. Of particular concern is a trading strategy that grew out of the option pricing model developed by the late Fischer Black and Nobel laureates Myron Scholes and Robert Merton. Used by market professionals, this strategy, known as option replication, requires mechanistic selling as stock prices decline and buying as stock prices rise. When a large enough number of investors engage in this type of trend-following "dynamic hedging," their trading demands can sweep markets along with them, elevating stock prices at some times and causing dramatic price drops at others. Capital Ideas and Market Realities uncovers the hidden risks these products pose for market stability and investor wealth.