Of First Importance

1 Corinthians 15:1-11
15Now I would remind you, brothers and sisters, of the good news that I proclaimed to you, which you in turn received, in which also you stand, 2through which also you are being saved, if you hold firmly to the message that I proclaimed to you—unless you have come to believe in vain. 3For I handed on to you as of first importance what I in turn had received: that Christ died for our sins in accordance with the scriptures, 4and that he was buried, and that he was raised on the third day in accordance with the scriptures, 5and that he appeared to Cephas, then to the twelve. 6Then he appeared to more than five hundred brothers and sisters at one time, most of whom are still alive, though some have died. 7Then he appeared to James, then to all the apostles. 8Last of all, as to one untimely born, he appeared also to me. 9For I am the least of the apostles, unfit to be called an apostle, because I persecuted the church of God. 10But by the grace of God I am what I am, and his grace toward me has not been in vain. On the contrary, I worked harder than any of them—though it was not I, but the grace of God that is with me. 11Whether then it was I or they, so we proclaim and so you have come to believe.

What does Paul say is "of first importance"?
Christ died for our sins...
There are myriad understandings of what this means. I take it to mean that Jesus was like a Jewish sacrifice: the power of his life was released at the crucifixion, and this power is available to us to assure of forgiveness, to enable healing and repentance. What does it mean to you?
...in accordance with the Scriptures...
The early church found Jesus everywhere in the Jewish Scripture, using their method of interpretation. Many in our day continue to do the same - many do not! One of the largest intellectual splits in the U.S. church involves whether one accepts modern advances in literature as applying to the Bible. The methods used in the first century were highly selective and subjective - using them, you can find pretty much whatever you want in Scripture. (One simple example of first century interpretation can be found in Matthew's use of Isaiah 7:14 - see http://fontes.lstc.edu/~rklein/Documents/adventa.htm#Advent4 for details.)
I certainly don't see Jesus death (and resurrection) "foretold" in the Scriptures (and yes, I'm quite aware of the myriad prophecies that are claimed to fortell Jesus). I do see Jesus as being both in continuity with and in opposition to the Jewish tradition. He quotes the Scriptures often, but very selectively. He's not afraid to say "Moses said... but I say...", nor is he afraid to say that Moses (not God) laid down a law "because of your hardness of heart". Primarily, I understand the meaning of Jesus' death to be very much in accordance with the Jewish understanding of sacrifice, which is markedly different from that of surrounding religions.
"...and that he was buried..."
The early church is quite insistent that Jesus actually died. He didn't just swoon. (Some folk, in an attempt to make the resurrection scientifically palatable, have claimed that Jesus didn't really die - he just fainted or went into a coma, and came out of it early Sunday morning.) If a crucifixion didn't kill you (and a one-afternoon crucifixion was not typically fatal - thus the breaking of the legs, to hasten asphyxiation and death), being wrapped in a shroud so that you couldn't breathe would presumably do the trick.
...and that he was raised on the third day in accordance with the scriptures,
"Christ is risen!" "Christ is risen indeed!" So shall the Church around the world proclaim this Sunday. I agree with Paul that without this belief Christianity is foolishness. Following most of Jesus' teachings could still make sense, but Christianity as a religion is built upon the belief that the spirit of Jesus Christ is available to us here and now as a living presense.
...and that he appeared to Cephas, then to the twelve. [and many others]
Those who learn that I take much of the Bible as story that contains truth but does not describe what literally happened (e.g., I don't think Genesis 1 and 2 describe the Big Bang very well, I don't think there was a literal Garden of Eden; I do think the universe is 13.7 billion years old, and that we evolved from other creatures) often claim "then how can you trust the Bible?" My short answer is "I don't, I trust God." But the longer one is: this passage of Scripture was written by a contemporary (Paul). It's, in part, a secondary source - "I handed on to you ... what I had recieved" - but it is very close (within a 20 years) to the events it describes. It's clear that Paul here is not writing metaphorically. That doesn't make what he says true, of course, but to state that one part of Scripture is metaphorical doesn't make the entire collection of books "false".

Paul definitely has an agenda here - he is preparing for the rest of chapter 15, which claims that life after death is not a false hope but is promised by Christ's resurrection. But the rest of his writings make it clear that Jesus' death and resurrection is, indeed, "of first importance" to him. What in Christianity is "of first importance" to you? Have you ever shared it with your Christian friends? How about your non-Christian friends?

Miscellaneous meanderings:
"Cephas" is "rock" in Aramaic; it is, presumably, the name that Jesus gave to Simon, translated as "Peter" (Greek for "rock") in the Gospels. I doubt anyone knows why Paul uses the Aramaic version - perhaps that is the one Peter normally used, and it is translated in the Gospels for the Greek reading audience; perhaps it is a slight dig? Paul accuses Peter of acting like a Judaizer when it's convenient.
Note that "the twelve" are different from "the apostles". The Gospels tend to treat "the twelve" and "the apostles" as the same group, but give them more than 12 names. Tradition says there were twelve, and overlaps the names, but here it seems likely that there were more than 12 apostles (in addition to Paul).
"One untimely born" is a polite but weak translation. When I was younger I thought Paul was claiming that he wasn't born at the right time to see Jesus in person, but this is flat-out wrong; Paul and Jesus were contemporaries. What the phrase literally means is "an aborted birth." Paul is calling himself a dead infant - stating in a graphic way the idea of verse 9.