Like it or not, Christians and Muslims are going to be seeing a lot of each other. Together they have nearly four billion adherents, making up more than half of the world's population.
Both religions are growing, with Muslims (now about 1.5 billion) increasing faster than Christians (about 2.2 billion) mostly because of birthrates. The adherents of both are global. Both touch every corner of the earth. Adherents of the two faiths are becoming neighbors.
Christians and Muslims have a great difficulty in understanding one another, which is understandable because they are structurally and conceptually different, variations dating back to their origins and their founders.
Neither Jesus nor Muhammad set out to establish a new religion. They each attempted to restructure the society and the religious practices that they found.
In the case of Jesus, he was born into a community that was controlled by a heartless economic system that had succeeded in corrupting the leadership of the dominant religion, Judaism. Jesus led a rebellion, not of swords but of ideas seeking to reform theological understandings.
When Jesus took his reform movement to Jerusalem, he was greeted as a nuisance and was killed by Rome's occupying authorities, supported by cooperating religious leaders. He was executed by being hung on a cross, a cruel and humiliating death that was meant to end his challenge to the powers-that-be.
Instead his followers turned the cross into the most powerful symbol in the history of Western civilization. Jesus was deemed the son of God.
To his followers, Jesus died on the cross for the sins of the world, a sacrifice that is celebrated in Christian worship as communion (or mass). Christians argue about the meaning of the communion service, but communion remains fixed as the heart of Christian worship centered on the death of Jesus on the cross.
While Christianity was the outcome of a failed reform movement, Islam was the result of a highly successful reform movement.
In the 7th century CE, Muhammad, a man of spiritual and social sensitivities, observed that his Arab people were constantly warring with one another and that wealth and the pursuit of wealth were driving people to terrible treatment of one another.
According to Muslim tradition, God spoke to Mohammad and gave him holy words to be shared with the Arab people. The message to the Arab communities was simple: "There is no God but Allah" and Allah's instructions were written down by Muhammad in a holy book, the Qur'an.
The people of Mecca responded to the message and the city was transformed. In a period of about 10 years, Mohammad and Islam had put down all challenges and were on the path to regional domination. In contrast to the failure of the Jesus revolution, the revolution led by Mohammad was highly successful.
However, Muhammad, who died only 10 years after writing the Qur'an, claimed no divine status for himself. He was the prophet chosen to pass down God's revelation. The revelation was what was central, with the Qur'an becoming Islam's unquestioned Holy Book. (In the Qur'an, Jesus is regarded as an earlier prophet, or messenger, from God.)
The central act of worship for Muslims is an act of obedience. Faithful Muslims are required to prostrate themselves in prayer to Allah five times daily, always facing toward Mecca. The great symbol of devotion is the Qur'an.
Because of their origins, the differences between Islam and Christianity are real. Christianity is symbolized by the cross and God's sacrifice of his only son, while Islam is symbolized by a Holy Book containing Allah's instructions. One calls for faith, the other calls for an act of obedience.