Many economists argue that a pure market economy cannot come about because people will always have incentives to use coercion (Cowen and Sutter, 2005; Holcombe, 2004). We maintain that these economists leave out an important factor in social change. Change can come about by altering incentives or preferences, but since most neoclassical economists ignore changing preferences, they too quickly conclude that change is impossible. History shows that social change based on changes in preferences is common. By recognizing that preferences need not be constant, political economists can say much more about changing the world.