This is just me, I am not saying I had some sort of revelation about it, but the Bible says that when Jesus died he went and peached in hell. I've also heard a known prophet say one time to make sure we are known in Heaven, Earth and in Hell, and I was taken to hell once to see something secret, so we, though Jesus, have some access to it. Maybe our spirits are preaching down there and we don't know it? Sometimes I think that people who died without Christ, will, somehow, still have a chance we don't know about or fully understand. Also, from my understanding, the more transformed we are on earth, the more aware we will be in Heaven. From my understanding, there will be people in Heaven who won't be able to enter the New Jerusalem, which makes me think, there will be some people who won't be fully aware of their capacity or identity in heaven (based on Revelations). But again, this is just theory. I rest in the reassurance that God made sure whoever died, had a chance to understand the gospel. If they didn't want to accept it, then I accept that was their decision.
