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: Slavery and Control of the Government. Throughout the first half of the 19th century, Southern politicians sought to defend slavery by retaining control of the federal government.
While the most common cause of the Civil war is said to be slavery, there were several other factors involved also. Although slavery was the major cause, so to speak, it was definitely not the only cause of the Civil War. As the former led to the latter, abolition of slavery and Civil War have become comparable terms.