"Who Do You Say That I Am?"
Why would Jesus ask his disciples, "Who do you say that I am?"
The Gospels do not directly explain Jesus' motive in asking the question. My opinion would be that Jesus was forcing the disciples to make a choice in their faith, to stop sitting on the fence and say once and for all who they think Jesus is. It is one thing to harbor a suspicion about something; it's quite another to speak it.
As we can see from Jesus' first question about what other people are saying about him, there was much confusion about Jesus' identity. The disciples of Jesus, up until that point, could have harbored any number of suppositions about Jesus. By directly asking what they think Jesus challenged them to look past what everyone else was saying and to profess what they had experienced during their time with him. Once we put something into words, we commit ourselves to that statement, and thus Jesus was most likely helping form the faith of the disciples.