Rev. Meg Barnhouse's sermon delivered on September 18, 2011. In the early days of Unitarianism, a group of friends formed what historians have called a genius cluster in Concord, Massachusetts. Ralph Waldo Emerson, Henry David Thoreau, the Alcott family, Nathaniel Hawthorne, and Margaret Fuller were giants in forming American culture and thought. How did this explosion of growth and influence take place? This is one of the stories of our heritage.