Christianity today reflects a wide variety of practitioners and beliefs in addition to a wide geographic distribution. The argument could be made that all Christians, however, have a few core unifying beliefs. Similarly, early Christians had a wide variety of practitioners and beliefs. Despite this, early Christians did not agree on core unifying beliefs.
Many of the things that we know about early Christian groups come from different scholars at the time. One of the scholars most often cited by historians is Josephus, an educated Jew who lived during the lifetime of Jesus (PBS, 1995). Based on his assessment, we know that Jesus was one of many wandering charismatic preachers of the time. These preachers were typically wiped out by Roman governors, while their followers were dispersed to prevent rioting. The unique thing, however, about the followers of Jesus was the way they responded to his crucifixion (PBS, 1995).
Part of the mythology that some followers adopt post-crucifixion came from the pagan groups that also existed in the area (PBS, 1995). The most clear example of this was the widespread adoption of mystery practices from Roman worship of the Persian god Mithras. Comparisons can be drawn between the seven initiations of Roman worship of Mithras and the seven sacraments of Christianity (Hopfe, 1994).
With the additional adoption of new beliefs, early cults and sects of Christianity could be identified based on which beliefs they held. The three most recognized groups of early Christians include the Jewish Christian movement, the Pauline movement, and the Gnostic Christian movement (Ehrman, 2005).
Jewish Christian groups were people who already practiced Judaism when they adopted Jesus as a religious figure (McGrath, 2006). They belonged to a reformation movement within the Jewish religion. This group is also divided into smaller communities. These smaller communities included the Ebionites, Nazarenes and many other groups (Ehrman, 2005). The Ebionites regarded Jesus as the Messiah and maintained Jewish law and rites (Cross & Livingston, 1989). The Nazarenes believed in Jewish tradition like the Ebionites, but also believed that Jesus was not only the Messiah but also the son of God (Cross & Livingston, 1989).
The Pauline movement, or Gentile movement, followed the beliefs and doctrines set forth by the apostle Paul. Many of the groups in the Pauline movement were later incorporated the larger Catholic Church, contributing to the apostolic tradition canonized by the organization (Ehrman, 2005). One Pauline group that would be considered heretical today practiced Marcionism. Marcionism is a belief system in which the Hebrew God of the old testament is representative of evil, while the Christian God is representative of good (Ehrman, 2005).
Finally, the Gnostics believed, like the Marcionists, in a dualistic view of the world. They believed that the material world should be shunned in favor of the spiritual world, and that both realms were under the rule of a single being who represented both good and evil (Hinnel, 1997). One of their most commonly recognized characteristics is the belief in a secret gospel of Jesus, suggesting that there are people who are destined to ascend while all others will only perish (King, 2005). Of particular note is the recent discovery of the Gospel of Judas (Cockburn, 2006), which is representative of Gnostic belief.
Cross, F.L. & Livingston, E.A., The Oxford Dictionary of the Christian Church. Oxford University Press, 1989
Ehrman, B.D., Lost Christianities: The Battles for Scripture and the Faiths We Never Knew. New Ed ed. N.p.: OUP USA, 2005.