The first step in protecting the environment is setting a goal: How clean do we want it to be? There is no “right” answer to this question, but whatever answer we choose, implicitly or explicitly, the costs of cleanup will be weighed against the benefits. Here, we explore three different cleanup targets, each comparing the costs and benefits in different ways: efficiency, safety, and sustainability. The focus is on both ethical and practical issues. We begin with a discussion of the utilitarian ethical framework that economists use and then explore two fundamental reasons why unregulated markets tend to produce too much pollution from any perspective. We then carefully look at the techniques that economists have developed to measure the benefits and costs of environmental protection, the strengths and limitations of the benefit–cost analysis, and the broader relationship between growth in material consumption, resource depletion, and growth in well-being. How much pollution is too much? This part of the book provides the tools to help you make up your mind.