Augustine in the context of "New Jerusalem"

Eternal return (or eternal recurrence) is a philosophical concept which states that time repeats itself in an infinite loop, and that exactly the same events will continue to occur in exactly the same way, over and over again, for eternity.

In ancient Greece, the concept of eternal return was most prominently associated with Empedocles and with Stoicism, the school of philosophy founded by Zeno of Citium. The Stoics believed that the universe is periodically destroyed and reborn, and that each universe is exactly the same as the one before. This doctrine was fiercely criticised by Christian authors such as Augustine, who saw in it a fundamental denial of free will and of the possibility of salvation. The spread of Christianity therefore diminished classical theories of eternal return.

Concupiscence (from Late Latin concupīscentia, from the Latin verb concupīscere, from con-, "with", here an intensifier, + cupere, "to desire" + -scere, a verb-forming suffix denoting beginning of a process or state) is an ardent longing, typically one that is sensual. In Christianity, particularly in Catholic and Lutheran theology, concupiscence is the tendency of humans to sin.

There are nine occurrences of concupiscence in the Douay-Rheims Bible and three occurrences in the King James Bible. It is also one of the English translations of the Koine Greek epithumia (ἐπιθυμία), which occurs 39 times in the New Testament.

Pelagianism is a Christian theological position that holds that the fall did not taint human nature and that humans by divine grace have free will to achieve human perfection. Pelagius (c. 355 – c. 420 AD), an ascetic and philosopher from the British Isles, taught that God could not command believers to do the impossible, and therefore it must be possible to satisfy all divine commandments. He also taught that it was unjust to punish one person for the sins of another; therefore, infants are born blameless. Pelagius accepted no excuse for sinful behaviour and taught that all Christians, regardless of their station in life, should live unimpeachable, sinless lives.

To a large degree, "Pelagianism" was defined by its opponent Augustine, and exact definitions remain elusive. Although Pelagianism had considerable support in the contemporary Christian world, especially among the Roman elite and monks, it was attacked by Augustine and his supporters, who had opposing views on grace, predestination and free will. Augustine proved victorious in the Pelagian controversy; Pelagianism was decisively condemned at the 418 Council of Carthage and is regarded as heretical by the Roman Catholic Church and Eastern Orthodox Church. For centuries afterward, "Pelagianism" was used in various forms as an accusation of heresy for Christians who hold unorthodox beliefs. However, more recent scholarship in both theology and religious studies has questioned how strongly Pelagius's beliefs differed from those of his opponents and from modern mainstream Christians.