The main question of the Gospel according to Mark is: “Who do you say that Jesus Christ is”? That there was a flesh-and-blood man named Jesus of Nazareth who once walked upon the face of the earth cannot be denied. The gospel writers were careful historians. Many early Christian writers wrote about him. Also several early secular writers spoke of Jesus as a historical figure: Tacitus, Pliny the Younger, Josephus, and Lucian of Samosata–all first or second century authors–mentioned Jesus in their writings.
Mark is concerned with this question. He told us right at the beginning who Jesus is. The opening words are, “The beginning of the gospel of Jesus Christ, the Son of God.” Only a few sentences later Mark told us about the heavenly Father confirming who Jesus was at his baptism. As Jesus emerged from the water the heavens were torn open, the Spirit of God descended upon Jesus like a dove, and a voice resounded that said, “You are my beloved Son; with you I am well pleased” (1:17). There is no room for equivocation: Jesus Christ is the Son of God.
As you read through the Gospel you see that so few understood who he is. Hardly anyone understood that he is the Son of God. There were a few who did understand: notably the demons and the centurion presiding over Jesus' crucifixion. Consider the irony!
His family did not understand. They thought he was crazy. In 3:21 we read about a large crowd gathering around Jesus seeking healing from him. When his family heard about this they went to seize him saying, “He is out of his mind.”
The people of his hometown did not understand. In 6:1ff we read about Jesus coming to Nazareth and teaching in the synagogue. The people had heard about the mighty deeds he had done in other places. They wondered where he had acquired his wisdom and power. After all, he was just the carpenter's son, and they knew his mother, brothers and sisters, and they took offence at him.
The Judean leaders did not understand who he was; in fact, they called him a blasphemer. They understood the claim that Jesus was making about himself, that he was the Son of God. At the trial the high priest put the question before Jesus: “Are you the Christ, the Son of the Blessed” (14:61). Jesus answered, “I am” (v. 62), at which the high priest accused Jesus of blasphemy and the Sanhedrin said that he deserved to die.
The disciples did not understand who he was. When Jesus calmed the storm they were filled with great fear and asked each other, “Who then is this, that even the wind and the sea obey him?” (4:41).
At one point the disciple Peter had a flash of insight and confessed Jesus to be the Christ. Jesus had asked his disciples who the people were saying that he was. They told him people were saying that he was John the Baptist, or Elijah, or one of the prophets. Then Jesus asked them, “But who do you say that I am?” Peter answered, “You are the Christ.” This is the question of the Gospel according to Mark. Note that Mark asked it near the centre of his gospel. It is a climax of a sort. Note also that when Jesus, upon Peter's confession, began to tell them what it meant that he was the Christ, viz., suffering, death, and resurrection, Peter took him aside and began to rebuke him. Peter's flash of insight was flash-in-the-pan!
Finally, yet about the disciples not understanding who Jesus was, no matter which ending of the four possible endings of Mark one accepts as authentic (see notes in a good study Bible or commentary), the disciples do not understand. Even after hearing about the resurrection they were afraid and Jesus upbraided them for their unbelief.
Some other people had flashes of insight into who Jesus is: The rich young man called him “Good Teacher” and Jesus replied by asking the young man why he had called him good considering that only God is good (10:17ff).
Blind Bartimaeus had a flash of insight. When he was told that Jesus of Nazareth was passing by he called out to “Jesus, Son of David.” He knew that Jesus of Nazareth was the messianic King.
“Legion” had such a flash. After Jesus had cast out of the man the legion of demons, Jesus told him to go and tell his family and friends how much the Lord had done for him; however, he began to proclaim in the Decapolis how much Jesus had done for him (5:19-20). Note also that the society of the Decapolis was a mixture of Hellenistic and Semitic cultures.
So we see that, besides a few flashes of insight, no people understood that Jesus was the Son of God. Besides Peter, the people who had the “flashes” were mostly social and/or racial outsiders.
Ironically, the demons did understand exactly who Jesus is. When Jesus confronted demons at the outset of his earthly ministry a demon cried out, “I know who you are—the Holy One of God.” Mark added in v. 34 that the demons knew Jesus. Yet other demons repeatedly fell down before him in defeat and cried out, “You are the Son of God!” Legion (the man filled with thousands of demons) shouted at “Jesus, Son of the Most High God” (5:7).
There was one human being who understood who Jesus was: the Roman centurion who presided over Jesus' execution. In 15:39 Mark told us that when the centurion saw how Jesus had died he said, “Truly this man was the Son of God.”
The unspoken question of the Gospel according to Mark is, “Who do you say that Jesus is?” Do you confess him to be the Messianic King, the Christ, the Son of the Most High God? When you read the opening words of the Gospel, “The beginning of the gospel of Jesus Christ, the Son of God,” do you say, “Yes and Amen!”?
That is who Jesus is. May all who read the Gospel according to Mark confess Jesus Christ to be the Son of God, the only Saviour.