As a Christian, it's weird hearing non-Christians describe Christianity. It's as if they've heard a single Bible verse, John 3:16, “For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life.” Non-Christians know "Jesus died for our sins" but their understanding of his death is as a poorly planned symbol. Why does somebody have to die? Doesn't God make the rules? And if he does, can't God make the "wages of sin" whatever he wants? Furthermore, how is it that one person can take the punishment for someone else? How do we know salvation isn't an afterthought? Might it be the case that Jesus died and a group of diehard followers invented "salvation" as a means of keeping the up the momentum of the Jesus movement?
From my own experience, it seems the most common, albeit disagreeable, answer has something to do with dismissing Levitical law as "cultural" and "not applicable in today's world." Even if that is true, there is a major flaw in that excuse: it isn't rooted in the Bible. No where in the Bible does it say Levitical law was cultural. If anything, it says the exact opposite. (Matthew 5:17-19) To be clear, the Bible says we are "dead to the law" (Romans 7) and in Acts 10, laws about food and who Jews may associate with are given a back seat in order to spread the gospel to Gentiles, but the Bible does not say the laws are flawed. They are and have always been good and deliberate commands from God. (Romans 7:12-13) When we dismiss parts of the law, we not only misrepresent the Bible, we appear to be cherry picking, waving our hands and manipulating the Bible to suit our purposes.
This question lies at the heart of so many questions. What happens to us after we die? Why did God put a forbidden tree in the garden of Eden? How can God send people to hell? They all boil down to, “Why did God make us?” Since "purpose" is such a broad topic, I am limiting my writing to the purpose of humanity at large and specifically how, in Christianity, our individual purpose is not something that is fulfilled after we die, but begins the moment we are saved.