Epiphany showcases the revelation of Jesus the Messiah to the world. Apparently, Jesus's contemporaries were expecting a Messiah more or less out of Marvel Comics. By contrast, today's readings (except the psalm, which taken literally is kind of bellicose and "must be understood figurative") show Jesus revealed also in humanness, kindness, and humility. (Even in Isaiah, the Servant gets knocked around but isn't destroyed.) The Jewish folks were expecting a political messiah, as in the Psalm. Today's Acts reading completes the all-nations theme, and ends the business about Jesus being for the Jewish people only.
Josephus tells us that John, who preached repentance, immersed people who were sorry for their wrongdoings, not literally to wash away the sins, but as the outward sign of something that had already happened internally. Horst Moehring, who was chief of Religious Studies at Brown, my New Testament prof, a major authority on Josephus, and a rowdy atheist, once wrote an article in which he argued (on the evidence of other ancient documents about the other religions of the Hellenistic age) that John literally believed that the sins were washed downstream. Another scholar misunderstood Horst and called him a fundamentalist, which Horst thought was extremely funny.
Secular scholars distinguish authentic from questionable (or worse) stories about Jesus based on a number of reasonable criteria. The strongest is probably: "The early church would not have invented stories which show Jesus acting in ways that might be understood as contrary to the church's teaching." Foremost among these "unquestionably authentic stories" is Jesus's having been baptized.
Why did Jesus allow Himself to be baptized, if baptism was for repentance? (1) Maybe he wanted to endorse John's ministry of repentance. (2) Maybe John's baptism wasn't so much to wash away the sins, as to wash away one's past. Jesus could never go back to being an ordinary carpenter. (3) Maybe Jesus knew more about being an ordinary human being facing ordinary temptations than He did about His own nature and mission. There have been times when I've made the confession of sin without being able specifically to name recent special acts of wickedness on my part.
I'd like to believe (3). It's much easier for me to relate to, and even to love, a fellow human-being who thinks "hey, I can't think of anything really awful that I've done, but now's a time in my life to admit I'm at least tempted and human, and get immersed like the other folks who are trying to live better lives." I carry this through Holy Week: It's much easier for me to really love a man let himself be tortured to death on our (i.e., my) behalf WITHOUT KNOWING, at least in specific terms, the final happy outcome.
Okay, okay... but give me too hard a time, and I'll accuse you of being a docetic.
The author of Acts (Luke?) could be interpreted by a heterodox Christian as saying that Jesus's special relationship with God began at the baptism. God "anointed" (echrisen, EKKH-reese-en, same root as "Christ" and "Christen") Jesus with the Holy Spirit and power (dynamei, doo-NAHM-ay, same as "dynamic" and "dynamite"). Our Unitarian brothers and sisters might want to preach on this text sometime.
A sect which claimed to have been the descendants of John the Baptist's movement were in existence at least until the year 500. They get mentioned in Acts 18:24; some of them became Christianized (and apparently some of the didn't, hence the survival). Apollos was one of John's folks, and he was considered "filled with the Holy Spirit" and preaching accurate Christian doctrine as far as it went. Priscilla and Aquila explained "the way" to Apollos. The passage tells me that the early Christians considered themselves to be the completion of John's movement. ("Oh! And at Pentecost, did the Holy Spirit come onto John's non-Christian disciples too? Or maybe on all people of good will?") Paul runs into John's folks again, and gives them a theological update, in Acts 19:1.
There's a story about a person who read in the Bible about one Jesus, who "went about doing good" (Acts 10:38). The reader realized that, until this time, he had been content "merely to go about".
Epiphany is the season for evangelism, and for bringing the good news to all nations. I once read a small book about a Marian apparition to a girl in the Netherlands. Of all the Marian apparitions (not that I'm an expert...) this was the one which impressed me the most. "The Lady of All Nations" appeared as a young Roman Catholic girl very much like Jewish Anne Frank, nicely dressed and with a globe. Like the other visions that have impressed me, this one was deliciously heterodox. Mary prophesied that the Bishop of Rome and Canterbury would meet in Rome (which they did), and said that the Anglican primate was a good man and that Rome should listen to him. I am not making this up. Mary also commanded that the practice of fasting before mass be abolished as superstitious. There was a prayer to Jesus too, which included the line "May the Lady of All Nations, who once was Mary, be our advocate." This didn't go over at all well with the Roman authorities, but Mary was insistent that this wording be used. For more on heterodoxy as authenticating this kind of thing, visit http://www.pathguy.com/theism.htm