“I’m here to promote my new book,” dryly announced history professor emeritus Gordon S. Wood as he faced a packed De Ciccio Auditorium. The mostly gray-haired crowd laughed; many, it appeared, were former students, familiar with the Pulitzer Prize–winning professor’s first-lecture tactic for thinning out an overenrolled course.

Alums may have recognized Wood’s talk as a new and improved version of the legendary final lecture of his early U.S. history course—a talk Wood describes as about “why America wants to spread democracy around the world.” He talked about the certitude with which a confident young America supported democratic revolutions elsewhere, its disillusionment when the Bolshevik upheaval led to socialism, and its revived idealism after the breakdown of the USSR and especially 9/11. The Arab spring that began in Egypt this March, made Wood’s thirty-year-old thesis seem especially topical.

Wood’s lecture—minus the Arab spring— forms the conclusion to his new book, The Idea of America: Reflections on the Birth of America, a collection of essays written over the past half century. After his forum, he signed copies of the book for a long stream of readers.