Modern industrial societies have achieved a level of economic prosperity undreamed of in earlier times, but on the view of the contemporary environmental movement, this prosperity has come at the cost of serious degradations to the natural world. For environmental advocates, problems such as resource depletion, air and water pollution, global warming, and the loss of biodiversity represent dire threats to the well-being of human societies and the planet itself. But just how serious are these threats, and how should we go about confronting them? Do environmental problems call for more extensive governmental controls over industrial activity, energy policy, and the like, or is it possible to find solutions by harnessing the incentives of the free market?