This is an interesting issue. First of all the Son of Man can be a confusing term. It can mean "a guy" (the literal meaning) - but after Daniel (circa 164 BCE) it was also used to refer to a cosmic judge figure (not God) who would come and judge the wicked, ushering in the end of normative history and the beginning of the kingdom of God, where the Jewish people would finally get some justice and there would be an end to their oppression.
So did Jesus think he was this cosmic judge? Bart Ehrman argues no. His points in summary:
* Jesus did use the term Son of Man as a central part of his message.
* In doing so he was referring to a cosmic judge of the earth who would come at the end of history to bring a cataclysmic end to the world as we know it, to destroy all the evil forces in the world that are opposed to God and that are making life miserable for his people.
* After this Day of Judgment the Son of Man would bring in a new kingdom on earth, a utopian kingdom of God.
* The ultimate root for this view of the coming Son of Man lies in a passage in the Hebrew Bible, Daniel 7:13-14, one of the earliest apocalyptic passages we have out of ancient Judaism.
* Different Jewish teachers in Jesus’ time understood the passage differently, and various ones of them had a differently nuanced understandings of who this “one like a son of man” was.
* Jesus’ view was distinctive but not entirely unique. Others too thought of the Son of Man as the cosmic judge of the earth.
* To show this was Jesus’ view requires an in-depth study of the way he uses the phrase in the New Testament Gospels, since he uses it in a variety of ways – and one has to determine which of these sayings about the Son of Man actually go back to Jesus himself (just as we have to determine at every point which of Jesus’ sayings are his, and which have been put on his lips by later storytellers after his death, passing along the traditions about him).
* There are several remaining fundamental points:
* When Jesus talked of this Son of Man, he was not referring to himself. Jesus was a man on earth speaking as a prophet about a cosmic judge who was soon to come from heaven above.
* After his death, Jesus’ followers believed that he had been raised from the dead and exalted to heaven.
* They also thought that Jesus was the messiah who had been sent from God in fulfilment of prophecy.
* But the prophecies about the messiah in the Jewish tradition were entirely about his exerting the power of God to destroy his enemies and rule as king over the nation of Israel.
* Jesus obviously never did that. On the contrary, he was a virtual unknown in his day, a rural preacher who offended the ruling authorities, was arrested, tried, condemned, publicly tortured and humiliated, and then executed for crimes against the state.
* His followers could plausibly maintain that he was the messiah only by insisting that he was coming a second time in glory, to fulfill the prophecies of the messiah who would destroy his enemies.
* Jesus was coming again from heaven to judge the earth in power.
Jesus, then, in the views of his followers after his death, was himself the coming Son of Man.
* And so they came to believe that when he had spoken of the Son of Man, he was speaking about himself.
* They adjusted his sayings about the Son of Man accordingly, and put sayings on his lips in which he described himself as the Son of Man.
* And that is why you have the conversation recorded above, in the passage of Matthew, expressed the way it is. In the older version, Mark, Jesus asks his disciples “Who do people say that I am” and when the reply he follows up with “And who do you say that I am.”
Matthew, who used Marks’ version as his source, altered the conversation slightly so there can be no question about Jesus’ identity: he first asks “Who do people say the Son of Man is?” This is a clear self-reference here (i.e., in *Matthew’s* version: he has changed Mark’s wording). When the disciples reply, he responds, “And who do you say that I am”
* Matthew has phrased the conversation in such a way that it is obvious to the reader that Jesus himself is the Son of Man. In that way, in every other place where Jesus refers to the Son of Man, everyone will understand that he’s talking about himself.
* Mark would have agreed that Jesus is the Son of Man, as did all the other Gospels. Mark simply did not make the matter as explicit as Matthew chose to do.
* It was not, though, the view of Jesus himself. It was actually quite contrary to his view.