Sadly I know the answer to this one
...well, the reformed, evangelical answer anyway, guessing the Catholic church has other ideas. I'd just like to point out I no longer believe any of this!

Everyone sins, which is to say everyone rejects God's rightful authority over our lives. And the just and rightful punishment for sin is death, nothing else is sufficient. And when I say death, I mean in the "forever cast from God's presence" type, not just the stopping breathing type. But there's a problem there, because that means that nobody will be found innocent. So what happens, we have Jesus coming and taking that punishment in our place so that we don't have to. Kind of a trading places thing, where he takes the punishment and God sees us as perfect and sinless.

That's the basic gist of it anyway, there's a whole load more detail but that's the rough idea.
(Liberal, Mon 23 Mar 2009, 0:52, Reply)