The City of God is a book of Christian philosophy written in Latin by Augustine of Hippo in the early 5th century AD. The book was in response to allegations that Christianity brought about the decline of Rome and is considered one of Augustine's most important works. Augustine wrote The City of God as an argument for the truth of Christianity over competing religions and philosophies. He argues that Christianity was not responsible for the Sack of Rome, but instead responsible for its success. Even if the earthly rule of the Empire was imperiled, it was the City of God that would ultimately triumph. As a work of one of the most influential Church Fathers, The City of God is a cornerstone of Western thought, expounding on many profound questions of theology, such as the suffering of the righteous, the existence of evil, the conflict between free will and divine omniscience, and the doctrine of original sin.