Glenn Beck is giving the work of think tanks millions of dollars worth of free advertising-obliquely. The title of his new novel is The Overton Window, and it refers to a theory of social change put forward by Joe Overton, former vice president of The Mackinac Center in Midland, Michigan. In brief, the theory holds that politicians choose from a narrow range of policies that are politically acceptable, but over time the window of political possibility can be shifted. The theory directs our attention to the importance of shifting that window in the direction of greater freedom rather than worrying about the latest election cycle. That’s what free market think tanks exist to do.