The air we breathe, the land we live on, the water we drink - these finite and incalculably valuable resources are also known as "the commons" - the shared wealth of the world. The ultimate purpose of cap and trade is to respect and preserve the commons, because a healthy world is the foundation for every culture, every nation, every living thing. In the case studies outlined here, cap and trade has been successful in protecting the commons largely because it respects three other important "commons":

Common Sense
Economies thrive on competition, and businesses respond to rewards. Given the freedom to innovate and a dynamic marketplace in which to operate, businesses will find the best and most cost-effective ways to solve their problems. Cap and trade respects these common sense marketplace principles.

Common Ground
Cap and trade programs have exceeded expectations when it comes to reducing pollution and protecting the environment. They have allowed businesses to meet goals at costs below predictions and to receive a fair price for their products. These programs have placed government bodies in oversight roles where they can focus on enforcement and compliance, and avoid the awkward position of telling an industry how to run its operations. The acid rain issue polarized environmentalists, industry leaders and government regulators for more than a decade, but cap and trade broke this logjam and provided common ground upon which all parties could jointly craft a solution.

Common Good
Problems such as air pollution don't stop at state or national borders. Increasingly, our environmental challenges are global in nature, shared by everyone on the planet. Greenhouse gases warm the atmosphere, no matter where they are produced on the globe. Removing a ton of these gases helps to slow climate change, whether that ton is removed in the East or West, Northern or Southern hemisphere. Cap and trade programs can take into account the big picture - the common good.