In 1855, Abraham Lincoln wrote a letter to his best friend, Joshua Speed. Speed was from a wealthy, slave-owning Kentucky family; Lincoln believed slavery was wrong. You are mistaken about this, Lincoln wrote to Speed. But, differ we must." One way for Lincoln to have dealt with his best friend, I suppose, would be to say you're a horrible person, you're morally wrong, and I shun you," says NPR's Steve Inskeep. "Lincoln did not take that approach, which I think might be a little controversial today."You might know Steve primarily for hosting NPR's Morning Edition. He also writes histories, and his newest book, "Differ We Must: How Lincoln Succeeded in a Divided America," takes a long hard look at Lincoln the politician: the man who went out of his way to build political consensus, even with people whose views he considered noxious. It's a case for why we should collaborate, and yes, compromise with people across the aisle – not because it's nice or the right thing to do, but because it makes our government work. Today on Throughline, a conversation with Steve Inskeep about the contradictions of Abraham Lincoln.