One major question within Christianity is this: What happens to the innocents who die before they are morally responsible for their actions and intellectually capable of becoming Christians? There are several possibilities, and below I will explain why none of them are acceptable.
It's hard to understate the extent of this issue for Christianity: it includes not only young children, but also the mentally handicapped and the unborn. The latter case is especially significant; I recently came across two statistics that should absolutely devastate anyone who believes that personhood begins at conception. This includes the many Christians who think that even fertilized human eggs (or zygotes) are imbued with an immortal soul. First, about 60 percent (one source says 30–70%; another says 60–80%) of all early embryos fail to implant themselves into the wall of the uterus and are lost. And second, a birthrate study recorded that only 126 out of its sample of 189 implanted embryos resulted in live births—one third were miscarriages.
Taken together, these two statistics mean that about 73.3% of all zygotes do not result in births. Let me put that another way. By the Christian definition of "person," nearly three times as many people have died naturally in the womb as have been born. Why would God let three quarters of all humans die before they even get a chance to live? And what happens to them afterward?
The problem is not limited to God merely allowing children to die; at times he is explicitly responsible for those deaths. He personally drowned millions of children in the Genesis flood (Genesis 7:21-23). In the tenth plague of Egypt he sent "the destroyer" to do his dirty work (Exodus 12:21-30). And on several occasions (e.g. 1 Samuel 15:1-9) he commanded the Israelites to kill children of rival nations along with adults.
As I've shown, countless billions of innocents throughout human history have died without having an opportunity to be "saved" by the usual means. Clearly, the question of their fate is one of the most important issues that Christians must face.
The Possible Answers
One possibility is that innocents go to hell. However, to punish them based on circumstances beyond their control is obviously repugnant and inconsistent with a good God. Second, they could meet some neutral fate—for example, they could simply cease to exist. This is a fairly sensible option, but it seems to contradict the idea of eternal souls, and (as we'll see later) at least one biblical passage opposes it.
Third, perhaps God knows what these children would have chosen if they'd had the chance and places them in heaven or hell accordingly. But this would entail sending them to an eternal reward or punishment based on decisions that they never actually made. And if God was somehow justified in doing this, then what is the point of this world in the first place? He could have simply placed everyone directly into heaven or hell and skipped the formalities.
Fourth, God might let these innocents choose whether to accept him after they die. But how exactly would this take place? Do they gain any direct knowledge of an afterlife or God himself? If so, why didn't God give all of us this evidence? Does God somehow provide them with only the sort of evidence they would have received on earth? If so, then once again, what is the point of our world in the first place? This scenario accomplishes the same goal in a much simpler manner.
Finally, maybe all innocents go directly to heaven, as many Christians believe. They speak of an "age of accountability" at which children become responsible for their sins. While there is nothing about this in the Bible, they often cite 2 Samuel 12:13-23, in which David implies that he will one day join his dead child in heaven. Of course, there's no particular reason to assume David's belief was justified, so this passage is inconclusive.
But beyond that, there's a serious problem with this view: Christians think this world exists to give people a chance to freely accept or reject God. They clearly believe that God greatly values this free will, as it's one of their most common defenses for the problem of evil (God allows evil so that people can freely choose good). If innocents who die before they can accept or reject him automatically go to heaven, they have made no such choice at all. The purpose of God's creation has been significantly undermined!
Another major issue is what heaven would be like for these innocents. Would an infant keep its limited mental capacity and do nothing but crawl around and drool? Would God miraculously grant them intellectual maturity? And if so, where would their personality come from, since it wasn't shaped by a lifetime of experiences? Christians might say that this newly matured being would retain the same "soul," but how could they be considered the same person as the drooling infant in any meaningful sense? What God would really be doing is creating a person from scratch.
In his omniscience and omnipotence, God should have been able to design our world such that everyone freely chooses to accept or reject him, without resorting to some other method to catch those who slip through the cracks. Yet he has both directly and indirectly robbed billions of innocents of their freedom to make that decision—in fact, far more have been deprived of that freedom than have actually used it. Based on this, I must conclude that the Christian system of salvation is flawed, makeshift, cobbled-together, and wholly inconsistent with the God who supposedly came up with it.