In response to Pelagius, Augustine adopted a theological system that included not only original sin (which Pelagius denied), but also a form of predestination.[1] Some authors maintain that Augustine taught the doctrines of limited atonement[2] and of irresistible grace,[3] later associated with classic Calvinism; however, others insist that Augustine's writings conflict with these doctrines.[1][4] Critics maintain that part of Augustine's philosophy might have stemmed from his expertise in Greek philosophy, particularly Platonism and Manichaeism, which maintained a very high view of a man's spirit and very low view of a man's body.