Dr. Benjamin Rush is not yet the subject of a Ken Burns miniseries, but he surely ought to be. The Philadelphia physician was a signer of the Declaration of Independence, an anonymous polemicist who helped inspire the Boston Tea Party and the editor of Thomas Paine’s wildly influential “Common Sense.” And, as detailed in a new biography by Stephen Fried, he both treated and became a close friend to several U.S. presidents. He personally brought Thomas Jefferson and John Adams back together after their friendship seemed permanently ended. In this episode, Fried discusses “RUSH: Revolution, Madness, and the Visionary Doctor Who Became a Founding Father.” Published last year, the book is just out in paperback.