Augustine of Hippo (354–430), who ultimately systematized Christian philosophy after converting to Christianity from Manichaeism, wrote in the late 4th and early 5th century: "But when I read those books of the Platonists I was taught by them to seek incorporeal truth, so I saw your 'invisible things, understood by the things that are made'." Until the 20th century, most of the Western world's concept of Manichaeism came through Augustine's negative polemics against it. According to his "Confessions", after eight or nine years of adhering to the Manichaean faith (as an "auditor", the lowest level in the sect's hierarchy), he became a Christian and a potent adversary of Manichaeism. When he turned from Manichaeism, he took up skepticism. In AD 386, he published "Contra Academicos" (Against the Skeptics).