the Roman emperors Antoninus Pius (reigned AD 138–161) and his adopted son and heir, Marcus Aurelius (reigned AD 161–180). The term (which derives from Antoninus's name) is often extended to include Commodus, son of Marcus Aurelius, joint emperor with his father from 176 to Marcus Aurelius's death in 180 and then sole emperor until his own death in 192. The period of the first two Antonine emperors (138–180) was one of great internal peace and prosperity, when the sense of security and the reconciliation of peoples was at their greatest throughout the Roman Empire. This period was chosen by the English historian Edward Gibbon as the beginning of his monumental and influential work History of the Decline and Fall of the Roman Empire (1776–88). See also Five Good Emperors.