Plutarch's Lives of the Noble Greeks and Romans, commonly called Parallel Lives or Plutarch's Lives, is a series of biographies of famous men, arranged in tandem to illuminate their common moral virtues or failings. The surviving Parallel Lives, contain twenty-three pairs of biographies, each pair consisting of one Greek and one Roman, as well as four unpaired, single lives. It is a work of considerable importance, not only as a source of information about the individuals biographized, but also about the times in which they lived.