Among medieval Christian theologians , Trajan was considered a `` virtuous pagan '' , while the 18th century historian Edward Gibbon popularized the notion of the Five Good Emperors , of which Trajan was the second . Among medieval Christian theologians , Trajan was considered a virtuous pagan , while the 18th century historian Edward Gibbon popularized the notion of the Five Good Emperors , of which Trajan was the second .