Variance in the human conscience requires that Christians either all be hard Calvanists, Universalists, or accept that God is Arbitrary -- else abandon the project of soteriology.
Simple argument: The human conscience doesn't reliably or consistently 'convict' people that they have sinned and are in need of a savior or forgiveness of God or anything of the sort. Paul's Natural Theology Arguments (Is it Romans 1&2?) are basically bunk as to any use of proving everyone knows they need atonement (since evidently everyone doesn't 'know' that).
We are left with a few possibilities:
Hard Calvanism -- God Chooses whom he chooses, and the Holy Spirit either guides your conscience to the truth or you live with a flawed mind that cannot perceive the need for salvation.
We cannot easily "soften" this, because the human conscience is not consistent at all. In other words, if the Holy Spirit comes along and knocks one day and you just don't perceive it as such in retrospect a week or a month or a year or a decade later, then he might as well not have come. Either he came irresistably (i.e. YOU were CONVINCED) or he needn't have bothered because it was identical to other glitches in your flawed human mind.
2) Universalism is true -- we are all Human. If God had wanted us to be a different Breed, he would have made us Angels, or Dogs or something. He knew what each of us was when he built us, and he knew our consciences were variable and malleable. It's all good, everyone goes to heaven (and probably everyone delights God RIGHT NOW as well).
3) God is arbitrary, and it comes down to something like, "Well, if you had this set of beliefs, then you get the pass into the door. If you didn't, either because you didn't come across them, or I didn't send the Holy Ghost at the moment you were going to really get it, then.... Well, so be it. I cannot make people with free will to my satisfaction otherwise. As a side effect, either eternal conscious suffering, or obliteration."
This situation is like the episode of Simpsons where Ned gets to the Pearly Gates and God says, "It was the Mormons, Ned. They were the one true religion." And he's just like, "Drat! How was I to know?"
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Each of these seem untenable, other than Universalism, yet universalism is among the least popular views in Christianity (and seems on the surface to be directly contradicted by Jesus's quotes). I'm left thinking the religion itself is bound to be incoherent as far as it is concerned with soteriology.