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.
The causes of the civil war have been a point of contention lately. First of all, its causes were economic. The North relied on the South's agriculture for its industrial wealth. When you add to this the problem with slavery, which was also economic but philosophical too.