Was secession really about slavery?

Since 1865, many defenders of the Confederacy have maintained that secession was not about slavery, but southern independence. Their proof is the “Confederate emancipation proclamation.” Our guest this hour, Professor Bruce Levine of the University of Illinois at Urbana-Champaign, is the author of “Confederate Emancipation: Southern Plans to Free and Arm Slaves During the Civil War (Oxford, 2006).