Twelve Apostles in the context of "Synaxis"

A bishop is an ordained member of the clergy who is entrusted with a position of authority and oversight in a religious institution. In Christianity, bishops are normally responsible for the governance and administration of dioceses. The role or office of the bishop is called episcopacy or the episcopate. Organisationally, several Christian denominations utilise ecclesiastical structures that call for the position of bishops, while other denominations have dispensed with this office, seeing it as a symbol of power. Bishops have also exercised political authority within their dioceses.

Traditionally, bishops claim apostolic succession and the historic episcopacy, a direct historical lineage dating back to the original Twelve Apostles or Saint Paul. The bishops are by doctrine understood as those who possess the full priesthood given by Jesus Christ, and therefore may ordain other clergy, including other bishops. A person ordained as a deacon, priest (i.e. presbyter), and then bishop is understood to hold the fullness of the ministerial priesthood, given responsibility by Christ to govern, teach and sanctify the Body of Christ (the Christian Church). Priests, deacons and lay ministers co-operate and assist their bishops in pastoral ministry.

Apostolic succession is the method whereby the ministry of the Christian Church is considered by some Christian denominations to be derived from the apostles by a continuous succession, which has usually been associated with a claim that the succession is through a series of bishops. Those of the Catholic, Eastern Orthodox, Oriental Orthodox, Church of the East traditions maintain that a bishop's orders are neither regular nor valid without consecration through apostolic succession. These traditions do not always consider the episcopal consecrations of all of the other traditions as valid.

This series was seen originally as that of the bishops of a particular see founded by one or more of the apostles. According to historian Justo L. González, apostolic succession is generally understood today as meaning a series of bishops, regardless of see, each consecrated by other bishops, themselves consecrated similarly in a succession going back to the apostles. According to the Joint International Commission for Theological Dialogue Between the Catholic Church and the Orthodox Church, "apostolic succession" means more than a mere transmission of powers. It is succession in a church which witnesses to the apostolic faith, in communion with the other churches, witnesses of the same apostolic faith. The "see (cathedra) plays an important role in inserting the bishop into the heart of ecclesial apostolicity", but once ordained, the bishop becomes in his church the guarantor of apostolicity and becomes a successor of the apostles.

Christianity in the 1st century covers the formative history of Christianity from the start of the ministry of Jesus (c. 27–29 AD) to the death of the last of the Twelve Apostles (c. 100) and is thus also known as the Apostolic Age. Early Christianity developed out of the eschatological ministry of Jesus. Subsequent to Jesus' death, his earliest followers formed an apocalyptic messianic Jewish sect during the late Second Temple period of the 1st century. Initially believing that Jesus' resurrection was the start of the end time, their beliefs soon changed in the expected Second Coming of Jesus and the start of God's Kingdom at a later point in time.

Paul the Apostle, a Pharisee Jew, who had persecuted the early Christians of the Roman Province of Judea, converted c. 33–36 and began to proselytize among the Gentiles. According to Paul, Gentile converts could be allowed exemption from Jewish commandments, arguing that all are justified by their faith in Jesus. This was part of a gradual split between early Christianity and Judaism, as Christianity became a distinct religion including predominantly Gentile adherence.

Paul, also named Saul of Tarsus, commonly known as Paul the Apostle or Saint Paul, was a Christian apostle (c. 5 – c. 64/65 AD) who spread the teachings of Jesus in the first-century AD. For his contributions towards the New Testament, he is generally regarded as one of the most important figures of the Apostolic Age, and he also founded several Christian communities in Asia Minor and Europe from the mid-40s to the mid-50s AD.

The main sources of information on Paul's life and works are Paul's letters and the Acts of the Apostles in the New Testament. Approximately half of its content documents his travels, preaching, and miracles. Paul was not one of the Twelve Apostles, and he did not know Jesus during his lifetime. Nonetheless, Paul was a contemporary of Jesus and personally knew eyewitnesses of Jesus such as his closest disciples (Peter and John) and brother James since the mid 30s AD, within a few years of the crucifixion (ca. 30–33 AD). He had knowledge of the life of Jesus and his teachings. According to the Acts, Paul lived as a Pharisee and participated in the persecution of early disciples of Jesus before his conversion. On his way to arrest Christians in Damascus, Paul saw a bright light, heard Christ speak, was blinded, and later healed by Ananias. After these events, Paul was baptized, beginning immediately to proclaim that Jesus of Nazareth was the Jewish messiah and the Son of God. He made three missionary journeys to spread the Christian message to non-Jewish communities.

Saint Peter (born Shimon bar Yonah; 1 BC – AD 64/68), also known as Peter the Apostle, Simon Peter, Simeon, Simon, or Cephas, was one of the Twelve Apostles of Jesus and one of the first leaders of the early Christian Church. He appears repeatedly and prominently in all four New Testament gospels, as well as the Acts of the Apostles. Catholic and Orthodox tradition treats Peter as the first bishop of Rome – or pope – and also as the first bishop of Antioch. According to Christian tradition, Peter was crucified in Rome under Emperor Nero.

The ancient Christian churches venerate Peter as a major saint and the founder of the Church of Antioch and the Church of Rome, but they differ in their attitudes regarding the authority of his successors. According to Catholic teaching, Jesus promised Peter a special position in the Church. In the New Testament, the name "Simon Peter" is found 19 times. He is the brother of Andrew, and they both were fishermen. The Gospel of Mark, in particular, is traditionally thought to show the influence of Peter's preaching and eyewitness accounts. He is also mentioned as Peter or Cephas in Paul's First Letter to the Corinthians and the Epistle to the Galatians. The New Testament also includes two general epistles, First Peter and Second Peter, which are traditionally attributed to him, but modern scholarship generally rejects the Petrine authorship of both.

The primacy of Peter, also known as Petrine primacy (from the Latin: Petrus, lit. 'Peter'), is the position of preeminence that is attributed to Peter among the Twelve Apostles.

Julius Schiller (c. 1580 – 1627) was a lawyer from Augsburg who, like his fellow citizen and colleague Johann Bayer, published a star atlas in celestial cartography.

In the year of his death, Schiller, with Bayer's assistance, published the star atlas Coelum Stellatum Christianum which replaced the pagan names of constellations with biblical and early Christian figures. Specifically, Schiller replaced the zodiacal constellations with the twelve apostles, the northern constellations by figures from the New Testament, and the southern constellations by figures from the Old Testament.

The Coelum Stellatum Christianum is a star atlas published in 1627 by Julius Schiller (c. 1580–1627), with the collaboration of Johann Bayer (1572–1625). In the treatise, which was published by Andreas Aperger at Augsburg during the same year as Schiller's death, pagan constellations were replaced with biblical figures and Christian motifs. Schiller replaced the zodiac constellations with the Twelve Apostles, the northern constellations with New Testament figures, and the southern constellations with Old Testament figures.

The planets, the Sun, and the Moon were also replaced by biblical figures: