One day in 1698, Robert Pyle of Pennsylvania decided to buy a black slave. The next night he dreamed of a steep ladder to heaven that he felt he could not climb because he carried a black pot. In the dream, a man told him the ladder was the light of Jesus Christ and would bear any whose faith held strong; otherwise, the climber would fall. Pyle woke that morning positive that he should eschew slaves and slavery, having equated the pot with the...