Which figure of speech is used in this text?
Common sense is not so common.
—attributed to Voltaire

 - anaphora
 - paradox
The text uses a paradox, a statement that might at first appear to be contradictory, but that may in fact contain some truth.
Common sense is not so common at first appears to be contradictory, as common sense refers to basic good judgment shared by most people. However, it contains some truth: many people do not use good sense or judgment in their actions.