The answer, if authentic, should be a timeless one. It shouldn’t be warped and shaped by culture.
It of course becomes problematic and confusing when we look around and attempt to find real Christianity out of a variety of denominations and practices. Taking an opinion poll will not help and, in fact, whatever we would find to be the most popular position would certainly disqualify it as being the authentic representation of truth on the matter.
However, as confusing as it is to attempt to figure out what it means to be a Christian, going back to the Christian church’s established written authority, the Bible, the answer is not difficult at all. Of course living the answer is a different matter entirely.
Here is the Apostle Paul’s answer as found in his first letter to the church at Corinth.
Let me now remind you, dear brothers and sisters, of the Good News I preached to you before. You welcomed it then, and you still stand firm in it.
It is this Good News that saves you if you continue to believe the message I told you—unless, of course, you believed something that was never true in the first place.
I passed on to you what was most important and what had also been passed on to me. Christ died for our sins, just as the Scriptures said.
He was buried, and he was raised from the dead on the third day, just as the Scriptures said.
1 Corinthians 15:1-4 (NLT)
The Good News, as this modern translation puts it is another way to say The Gospel.
A Christian is someone who truly believes the gospel and lives based on it being true.
Paul tells us in this passage what the gospel is.
Christ died for our sins, just as the Scriptures said. He was buried, and he was raised from the dead on the third day, just as the Scriptures said.
That’s it. Everything comes out of this. If you believe in all sorts of things including the existence of angels and devils, but you don’t believe this, you are not a Christian.
If you only believe this and everything else about the Bible and religious dogma are completely unclear, you are a Christian.