I never stopped to analyze why the disciples fell silent when Jesus asked what they had been arguing about ... I didn't have to. I always knew it was because they were ashamed without thinking about it. As any of us would feel when caught in such a moment. It takes looking at things through Jesus' eyes sometimes to see things clearly.
When he asked them what they had been arguing about they had nothing to say. It was the silence of shame. They had no defense. It is strange how a thing takes its proper place and acquires its true character when it is set in the eyes of Jesus. So long as they thought that Jesus was not listening and that Jesus had not seen, the argument about who should be greatest seemed fair enough, but when that argument had to be stated in the presence of Jesus it was seen in all its unworthiness...
Jesus took this very seriously. It says that he sat down and called the Twelve to him. When a Rabbi was teaching as a Rabbi, as a master teaches his scholars and disciples, when he was really making a pronouncement, he sat to teach. Jesus deliberately took up the position of a Rabbi teaching his pupils before he spoke. And then he told them that if they sought for greatness in his Kingdom they must find it, not by being first but by being last, not by being masters but by being servants of all. It was not that Jesus abolished ambition. Rather he recreated and sublimated ambition. For the ambition to rule, he substituted the ambition to serve. For the ambition to have things done for us he substituted the ambition to do things for others.
The Gospel of Mark
(The Daily Bible Series, rev. ed.)