A theorem is a short pithy - sometimes - statement that describes a big idea. In this case, the big idea is that we can understand how laws work in a single sentence or two.And having a very concrete way to understand how laws work, we can use that knowledge to make laws work better. We can use that knowledge to help us design policies that achieve more of our societal objectives.We can categorize our societal objectives into buckets, such as Efficiency and Distribution. When we look at society's goals in terms of these categories, we can learn to balance them better, using the levers of law, levers, such as incentives and penalties.Learn how to use those levers best and how they relate to objectives, and we can meet more of our societal goals.This book takes a law review article, published at Bocconi University School of Law, and releases it as a book. The article is a clarification of the sixth most-cited law review article of all time, that of the former dean of Yale Law School, one of the founders of the field of law and economics, and Second Circuit Court of Appeals Judge, the Honorable Guido Calabresi.It is offered to the general public and the president of the United States to help us create better, more balanced policies.