Board Thread:General Discussion/@comment-29082320-20160731164526/@comment-27701762-20160731181519

MCSquared wrote: I agree. But doesn't a human soul persist outside the body after death? Just because Asriel absorbed it doesn't mean it wouldn't still do that. But I do agree with your last point, I don't know what I was thinking. It does persist, but it is never stated how long the soul continues to exist. One thing I've always pushed is that it has to perish at some point, as otherwise there would be billions of human souls flying about on the Surface. When humans and monsters lived together, at some point even a few monsters should have absorbed a human soul, perhaps even simply by accident.

The containers for the human souls presumably preserve them as well, preventing them from collapsing or breaking apart or whatever it is that causes a soul to die. Chara's soul, not being in a container for who knows how many years after their death, could very easily have dissipated long before Frisk ever enters the Underground.

If not, then you would think that the monsters would be on the hunt for a floating human soul, since it would be all they need to break down the barrier.