riddle - separate with a riddle, as grain from chaff screen sift, sieve, strain - separate by passing through a sieve or other straining device to separate out coarser elements; sift the flour
Causes of the Civil War: Abolitionism. The issue of slavery was further heightened by the rise of the Abolitionist movement in the 1820s and 1830s. Beginning in the North, adherents believed that slavery was morally wrong rather than simply a social evil.
Causes of secession. The causes of the Civil War were complex and have been controversial since the war began. James C. Bradford wrote that the issue has been further complicated by historical revisionists, who have tried to offer a variety of reasons for the war. Slavery was the central source of escalating political tension in the 1850s.