Constantine I, sometimes called St. Constantine or Constantine the Great, was Roman Emperor in the early fourth century CE. During his reign, Christianity had begun to cement itself as the dominant religion of the Roman Empire. In response, Constantine first legalized Christianity and ended the persecution of Christians, and then converted shortly before his death; his baptism was one of the last things he did.

The gospels are descriptions of the life of Jesus Christ found in the New Testament of the Christian Bible. The four most famous ones are the gospels of Matthew, Mark, Luke, and John. Peter is famous for different reasons; the Catholic Church generally considers him to be the first Pope, and it is said that he is "the rock upon which Christ's church was built."

The Nicene Creed was issued in 325 CE and is the earliest known attempt to officially standardize the practice of Christian faith. It essentially stated, "We are Christians, and this is what we believe." It can be seen either as a cornerstone of the Christian faith or as the first in a long line of attempts to imbue Christianity with the power of secular authority.

The leader of the Eastern Orthodox Church was (and, depending on who you ask, still is) called the Patriarch. The Eastern Orthodox Church was centered in Constantinople and the Bishop of Constantinople as generally held the title of "first among equals" or the Patriarch. 

The Papal Bull Unam sanctam was issued by Pope Boniface VIII in 1302. It is notable for proclaiming the unity of the Catholic Church and, more significantly, the absolute authority of the Church in both spiritual and secular matters. It can be understood as part of a general trend in pre-Reformation Europe to try and solidify and extend the temporal power of the Catholic Church.

Paul the Apostle was a Jewish Roman citizen who, for reasons shrouded by the politicization of Christianity, came to believe in the divinity of Jesus Christ in the first century CE. He is more responsible than any other man (including Jesus) for spreading the faith of Christianity around the world. He wrote letters to Jews and Romans alike, as well as other religious and ethnic groups and travelled widely spreading the Christian gospel. Many historians consider that without the dedicated early influence of Paul, Christianity might have remained a small sect of Judaism, although this is impossible to determine with any certainty.

The Edict of Milan, issued by the Roman Emperor Constantine I in 313 CE, ended the state-sponsored persecution of Christians within the Roman Empire. It made Christianity legal in Rome and all of its provinces.

Christianity is by far the dominant religion of South America, but Catholicism in particular is followed by more than fifty percent of the continent.

Shortly after the death of the prophet Muhammad, the growing Islamic faith was fractured along ideological lines. The two groups that emerged, and have continued as distinct groups ever since, were the Sunnis and the Shi'ites (sometimes just Shias). Shi'ites believed that the Caliph should be led by the cousin of Muhammad or someone directly related to him. The Sunni believed that his advisor should rule the Caliphate and favor choosing a leader based on more meritocratic means.

Sharia law exists in many countries in the Islamic world. In a country governed by Sharia law, the laws of the nation reflect the laws and tenets of Islam as laid out in the Quran and the hadith.