If humans can imagine life before birth, why is life after death so difficult to imagine?

I'm not entirely sure I accept the assumption of your question: Is it really any more difficult to imagine life after death than life before death? Many philosophers have argued that it is difficult to imagine being dead because the act of imagination requires that one be alive. In other words, any attempt to imagine being dead is thereby a failure, some have argued. In imagining oneself dead, one must presuppose that there is a consciousness (a living one, presumably), so one cannot coherently imagine being dead — at least if that means imagining oneself being dead. Now if that's correct, then one similarly could not imagine the past before one existed. After all, in attempting to imagine the past, that would require you to be conscious and to be alive, etc. Of course, one might take this reasoning to show that it's not any harder to imagine life after death: Since we can imagine what existed before our birth, we can equally well imagine life after death. So I'm not entirely convinced of the...

Is it irrational or illogical to say that dead people can have their possessions "stolen"?

I gather that the worry behind your question is whether the dead really have "possessions" to be stolen: How can a dead person "possess" something? After all, they can't hold it, see it, use it, etc. But it's worth keeping in mind that stealing amounts to taking something that properly belongs to another — something in which that person has a property right . And having a property right and all that entails — having the right to preclude others from using an object, most importantly — does not seem to turn on our physical relation to an object. Whatever moral claim I have on my house, for example, doesn't turn on my actually being present in the house: My property right in the house is, as Kant put it, a matter of "intelligible possession". Others don't have the moral permission to occupy or use my property even when I am not using it or am not in physical possession of it. So I don't see that the fact that the dead are, well, dead and so can't possess their property in a literal sense is any...