Marc-William Palen is a historian and author of "Pax Economica: Left-Wing Visions of a Free Trade World"; he's on the show to discuss how free trade was once not the purview of neoliberals and free-traders, but rather a varied group of left-wing ideologues, from pacifists to georgists to feminists, and how these strains influenced key aspects of super-national institution-building, but foundered against the cold war and American hegemony. What can we learn as the modern GOP invokes McKinley-era tariffs as a new model?