The rise of the Christian Church to c.300 CE

Render unto Caesar that which is Caesar's and unto God that which is God's — The Bible

If one is to understand Western Civilization, one has to understand Christianity and the history of the Christian Church.  No single faith or institution has had a more profound impact on Western Civilization than Christianity.  However, many of its influences may not be so readily apparent because they are so deeply rooted in our past and therefore are harder to recognize. One example is the work ethic that traces its roots back to medieval Christian monasteries.  Other examples abound, but suffice it to say that the Christian heritage is a significant part of our culture today, whether or not we belong to the Christian faith.
During the Middle Ages, the influence of Christianity was much more obvious.  In fact, Christianity played such a dominant role in medieval life and culture that we still refer to the Middle Ages as the Age of Faith.  During that time, the art and architecture were primarily religious in nature.  The calendar was the Church calendar whose holidays (holy days) were those of the Christian faith.  The daily lives of the people, even their diets, were largely controlled by Christian dictates.  And politics were tightly interwoven with religion and the Church.  Christianity, which traces its beginnings all the way back to the time of the Roman Empire, is still thriving as one of the world's great religions.  Therefore, it is a major bridge linking the ancient world and its civilization to the medieval world and ultimately our own.
In its basic form, Christianity is a simple religion centering around the brief life of a humble Jew, Jesus Christ.  According to Christian dogma, Jesus was the Son of God, but miraculously born in human form to a virgin named Mary.  For several years he performed various miracles as proof of his divinity and preached a simple but profound doctrine of love and forgiveness, faith in God, and penitence for our sins.  At the age of 33, Jesus was brutally executed on a cross because of his teachings.  However, on the third day after his execution, he supposedly rose from the dead, seen as further proof of his divinity.  Forty days later, after appearing to other disciples and followers, he ascended into Heaven.  He said that sometime in the future he would return for a final judgment day whereby the dead would be resurrected and go either to Heaven or Hell according to their faith.
Christianity is a monotheistic religion (i.e.- believing in just one god) that is derived from Judaism.  The God of the Jews in the Old Testament is also the God of Christianity.  However, there is one aspect of Christian theology that has confused people down through the ages and led to untold controversy and even bloodshed.  That is the belief that the god of Christianity is a triune god or Trinity.  In other words, there are three aspects to God, but all are parts of one united god.  They are: God the Father and creator; Jesus Christ, his son who came to earth as a human in order to save us from our sins by giving up his life on the cross; and the Holy Spirit which inspires us with faith. Through the years, people have disagreed, at times violently, over the exact nature of each of these aspects and how they relate to one another.  The various points of view and arguments to support them are too subtle, involved, and oftentimes confusing to relate here, although they would emerge from time to time with tremendous impact.

Early history (c.30-3ll C.E.)

Christ's ministry left two things of vital importance to the later success of Christianity.  One was an appealing message of love, forgiveness, and eternal salvation for all people.  The other was the mission for Christ's apostles and all Christians to spread this new faith.  After Christ's departure, his followers started spreading his message in order to win new converts to the faith.  At first, preaching this message was confined to Jews, and the ruling Romans saw it as merely a sect or offshoot of the Jewish religion.  But a critical turning point in Christianity came with St. Paul of Tarsus, who saw Christianity as a religion for all peoples: Jews and Gentiles (non-Jews).  Therefore, he started spreading the word of Christ throughout the Roman world.
Thanks to its message and this preaching, the Christian religion grew in popularity slowly but steadily during its first century and a half (c.30-180).  Hollywood and popular imagination have romanticized and exaggerated the persecutions of the Christians during this period.  The truth is that Christianity during this time was still a relatively minor religion that drew little attention to itself from the Roman authorities.  There were occasional persecutions in these early years, not so much for the Christians' religious beliefs as their refusal to worship the Roman emperor and state gods.  Such worship was more like a pledge of allegiance than a religious act to most Romans, and refusal to do it was seen as an act of treason.  The Christians could have freely practiced their religion if they would only have paid the empire this worship.
However, unlike most other ancient religions where the religion was intimately tied up with the state and society as a whole, Christianity was a very personal religion that drew a sharp distinction between what one owed to the state on the one had and to God on the other.  Therefore, Christians refused to worship the state gods and that was where they got into trouble.  During the Pax Romana, the persecutions were few and intermittent, and most Christians could practice their religion with little or no interference.  Times were good and the authorities saw little harm coming from the odd habits of this minor sect.  In the third century all that changed.

The great persecutions

The third century was a time of intense anarchy.  Civil wars, barbarian invasions, and plague wracked the empire from end to end and threatened its very existence.  This seems to have affected Christianity in two very different ways that both worked ultimately toward one end.  First of all, the widespread troubles of the time caused many people to question the truth of their old pagan religions whose gods did not seem to be protecting Rome anymore.  Consequently, people started turning to new, more emotionally satisfying salvation religions to comfort them in such troubled times.  Christianity was just one such religion that gained converts during this turmoil.  Other cults worshipping the Persian Mithra, Asia Minor's earth goddess Cybele, and Egypt's Trinity of Isis, Horus, and Osiris also gained in popularity.
The second effect of the third century anarchy was more intense persecutions of Christians.  As long as the Empire was peaceful and prosperous, the refusal of the Christians to pay homage to the emperor and state gods was usually overlooked.  However, when things started falling apart, many Romans blamed the Christians for abandoning the old gods who in turn abandoned Rome.  The late third and early fourth centuries saw the most intense periods of persecutions, the worst coming under Diocletian and his successors from 303 to 3ll C.E.  Ironically, the persecutions helped the Christian Church, because they gave the Christians publicity that won them widespread sympathy and many new converts.  Consequently, right on the heels of its darkest hours of persecution came the Church's greatest victory: legalization and acceptance as the virtual state religion of the Roman Empire.

Constantine and triumph of the Church

The man who gave Christianity its big break was the emperor Constantine.  Legend has it that on the eve of a major battle against a rival for the throne, Constantine saw a vision of a cross in the sky with the words: "In this sign conquer".  Taking this as a message from God, Constantine placed a Christian emblem on his troops' shields and then won the battle.  However true this legend may be, the fact is that in 3ll, Constantine declared toleration for Christianity in the Western half of the Roman Empire.  When he took over the eastern half in 323, he also legalized it there.  From this point on, the Christian Church quickly became the dominant religion in the Roman Empire, largely from the favor bestowed upon it by Constantine and his successors.
The question arises as to why Christianity triumphed over other competing salvation religions.  Besides strong state support, there are five main reasons.  For one thing, it was exclusive.  Unlike most ancient religions which tolerated other faiths, the Christians said a person could belong to only one faith, Christianity, and be saved.  Such a belief naturally scared many people away from other competing faiths.  Second, Christianity actively sought converts.  Most other religions were there for other people to accept, but did not go out of their way to gain new members.  In sharp contrast to this, Christianity did seek new members, which gave it a decisive edge.  For another thing, Christianity was secretive and treasonous.  As seen above, this led to persecution, which led to publicity and popularity.  Fourth, from the reign of Constantine onward (with the brief exception of Julian’s reign), the Church received strong state support that put increasing pressure on pagans to convert until Theodosius I shut down all pagan temples in 393.  Finally, Christianity was well organized much along the lines of the Roman Empire.  As the faith spread across the empire, it especially caught on in cities.  Consequently, each city, which was already a center of Roman administration, became a Christian center as well under a bishop.  Each province, besides having a governor to rule it, also had an archbishop to rule the affairs of its bishops in the different cities.  Diocletian had divided the empire into four large districts called prefectures.  The Church, similar to this, had five main centers where Church patriarchs resided.  Four of these centers (Constantinople, Jerusalem, Antioch, and Alexandria) were in the East, reflecting where Christianity's main strength was then.
The fifth patriarchal center, Rome, was destined to become the most influential for several reasons.  First of all, it was the capital of the empire, giving it a good deal of prestige.  Second, Peter, the most important of Christ's disciples, had started Rome's first Christian congregation, which also gave Rome prestige.  Finally, after 600 C.E., Rome was free from the control of the Eastern Roman (Byzantine) emperors.  This made life more dangerous for Rome's popes (patriarchs), but it also gave them more freedom to expand their influence when more peaceful times came after 1000 C.E.