Why are there so many disagreements even among Christians?

The naive answer:

Only true Christians live correctly and will ascend to heaven.

The problem with the naive answer:

There is no way to identify “true” Christians. Each sect believes they are the one sect that has the true and correct understanding of how Christians should live.

The scholar’s answer:

Different sects of Christianity developed in isolation from one another in the early days of Christianity. This allowed them to evolve independently and adopt different truths and ways of living. Each also altered Christianity to fit better within their culture. The Catholic Church was established to attempt to reconcile all the differences and provide a single source of authority, but abuses by the Church led an educated few, such at Martin Luther, to rebel and the Church broke off a Protestant branch which quickly splintered into hundreds of branches. Some practices that have led to separations are not covered in the Bible at all.

Here are a few examples of disagreements between branches of Christianity:

  • Fundamentalists believe every passage in the Bible is the literal truth. Most Christians do not believe this.
  • Most Christians believe the Bible is inerrant, but some do not.
  • Some Christians pray to humans (saints) such as Saint Peter and Saint Paul. Most do not.
  • Some Christians believe that having faith in God is enough to get into heaven, others believe you must have faith but also do good works.
  • Some Christians believe that Mary, the mother of Jesus, was born without sin and can be worshipped.
  • Some Christians believe angels are active among humans.
  • Most Christians believe there is a hell for bad people to go to after they die, but many believe there is no hell, just no place in heaven for bad people after death.
  • Some Christians believe the devil is an active agent in our society, pushing individuals to do bad things, most do not believe this.
  • Some believe children should be baptized, others believe baptism should wait until you are an adult and can choose it for yourself.
  • Some believe in a sacrament of Communion, during which members consume the body and blood of Jesus, others do not.
  • Some believe women can be preachers or ministers, others do not.
  • Some believe LGBTQ people can be accepted, others think they should be forced to change who they are.
  • Some believe they should handle deadly snakes each Sunday at church to prove their faith in God.
  • Some believe Jesus came to America after he left Israel. Mormons
  • Some believe it is wrong to accept modern medicine, or to visit a doctor for any reason, or to use vaccines. Jehovah’s Witnesses, Christian Scientists, and Others
  • Some believe it is wrong to use electricity. Amish

Logically, we can conclude that there is no way to identify which set of teachings is the truth. The Bible has failed to adequately provide the answer to many debates. Differences will remain until the end of time or until one philosophy forcefully suppresses the expression of alternative ideas. Many wars of the last millenium occurred between different sects of Christianity and the wars were fought partially to promote the differing beliefs of one sect over another.

Some references for further research: