"Why is it reasonable to believe in prisons, but not in the hell?"

[FlatAssembler]

Pretty hard to reoffend in a prison.  Even so, when people get out they can reoffend - but unless we're talking about killing and or imprisoning a thief for life....there's really no stopping that.  

I'm gonna hit the pause button here.  Are you searching for ways to salvage your objections to the reality of prisons, or your arguments about prisons unreality by their lack of utility or effectiveness?  

Bad prisons that aren't effective or don't work are still prisons that exist.  You understand that, right?  You can't cogently object to prisons by what effect (or effectiveness) prisons have so long as you maintain that there aren't any prisons to refer to.........

And hell not being justice is also not a valid argument against the existence of hell?