When Jesus said, "Believe in me," did he mean "believe in me" or did he mean "believe in me"?
There is a subtle difference, but it is, in my opinion, what separates the three main strands of Christianity.
Jesus could have been saying, "Believe that I exist," or he could have been saying, "Believe that I will not lead you astray." Evangelicals define "belief" as the former and devote their lives to getting people to believe that Christ exists and is the Son of God. Catholics define "belief" as the latter and although they believe in the existence of Christ and that he is the Son of God they place the following of Christ's commandments above all else. Liberals may believe in the existence of Jesus and that he is the Son of God, but their belief in Jesus as a reliable paradigm of how they should live their lives is not dependant on his reality or divinity.
So when a Christian says to other Christians, "We all believe in Jesus Christ, don't we?" the answer he receives will be most likely, "Yes." But the chances are that such a response contains at least three different interpretations of the word "believe." This is fine when Christians are just trying to exist in the same organisation as each other, but it is extremely problematical when Christians try to work together, especially when it comes to mission. This is because the objectives of the participants will be completely different.