Matthew: I don’t think so. If I remember right, you think life is ultimately for happiness right? So why not drug the water supply? That would make loads of people happy.
Simplicio: They wouldn’t really be happy! It would be an illusion!
Matthew: So it’s a new drug that makes their brain look exactly like a genuinely happy brain.
Simplicio: Well actually it’s not just happiness I value. The way to happiness is important too.
Matthew: Exactly. And it’s not just salvation I value. The way to salvation is important too.
Simplicio: But that’s different!
Simplicio: If the child grows up, xe may turn out evil and go to hell.
Matthew: So will you support drowning her?
Simplicio: No, but I don’t believe in an afterlife, so it’s not my problem.
Matthew: It is. What if she turns out evil and tortures a dozen people to death?
Simplicio: Then it’ll be the torturing that’s bad, not that xe lived.
Matthew: Likewise, it will be the damnation that’s bad, not the life.
First, a stylistic point: virtually all attempts philosophical dialogues suck. That includes you, Plato (see: the Plato entry in proofs that p).
But anyway, on the substance: the ending seems obviously very weak. Most people would say that child lives + child doesn’t torture anyone to death > child dies. But it also seems like child dies > child lives and tortures a dozen people to death. For nonconsequentialist reasons, many people would pass on a hypothetical opportunity to go back in time and kill Hitler as a child, but if you somehow knew that a random child who died last week would have grown up to be a serial killer, that sounds like a lucky break to me.
I’m less sure what to say about the claim that it really, really matters how you get to heaven. I don’t find typical religious accounts of why heaven is (supposedly) so great, and what the criteria for getting there ought to be, very convincing in the first place so it’s hard to know what to say about variations on the scheme.
However, it doesn’t seem to fit with the things believers typically say about how great heaven is when not trying to solve these problems. “How you get into heaven is so important that it’s worth having a lot of people risk hell” seems like something that would hardly ever occur to a believer except when they’re trying to dodge a problem like this.