The author provides a preview of the Pelagian controversy from early church history, which involved Augustine and Pelagius (a later development of Pelagianism became known as semi-Pelagianism). The controversy in question centres around the nature of the fall of man, saving grace, and the will of man. Other important events included are the Council of Ephesus in 431 and the Council of Trent.
Source: Ligonier Ministries, 2005. 3 pages.