On March 4, 1865, in his second inaugural address, Abraham Lincoln called the country’s 4 million slaves “a peculiar and powerful interest. All knew that this interest was somehow the cause of the war.” Lincoln’s use of “somehow” suggests not uncertainty about the importance of slavery, but an awareness that the institution meant different things to different people. To Southern whites, it was a way of life to be defended, but their levels of dependence or even support for slavery varied by individual and by and within regions. To Northern whites, it might be minimally important, or a threat to the white man’s labor, or the South’s means of controlling America’s politics, economy, and society, or central to their own prosperity. To say that slavery caused the war oversimplifies the issue; to say it played a minimal or limited role in Southerners’ decision to secede from the Union, and the Northern and Southern decisions to fight, ignores reality.