The Academics (also known as Skeptics or Academic Skeptics) were a group of philosophers who believed that humans are incapable of knowing anything for certain. The philosophy, which traces its roots back to Ancient Greece, received its clearest articulation through the writings of Roman philosopher and statesman Cicero, its most notable adherent. Augustine encountered the Academics when he lived in Rome, a time of great personal uncertainty that made their ideas attractive to him. However, he ultimately abandoned this philosophy, certain that there were spiritual truths to be found if pursued with sufficient time and effort.

Manicheism (also written as Manichaeism) was a major religion that emerged out of the Sasanian Empire (modern Iran) in the third century CE. Following the ministry of an Iranian prophet named Mani, Manichees (also referred to as Manicheans or Manichaeans) believed in a dualistic universe in which a good, spiritual god of light battled against an evil, material god of darkness. Manicheism incorporated the teachings of figures as diverse as Buddha and Jesus and was viewed as a major threat by much of the Roman world, because of both the ways Manichean teachings challenged mainstream religious values and the religion’s association with Persia, Rome’s longtime rival.