User blog comment:Jartsa67/question about souls/@comment-6637171-20130829155320

I think it has to do with the fact that when demons possess humans, they become corporeal. I mean their actual form is Smoke. You can't touch/kill smoke, right?. Also I'm just guessing here, that the knife is only targetted at demons. The humans are collateral damage. You are first stabbing the vessel. I mean a knife stab can killl anyone. Also, the soul is the demon. There is no demon "soul" (Plutus reminds Crowley of this fact in 8X02). I think they simply cease to exist. They don't go to Heaven because they were destined for Hell. Unless more info can be learnt from the show, we may never know what actually happens to the vessel's soul or the demon.