Everyone is so quick to assume that when they see a person that is see through or otherwise otherworldly, that they must be the continuing existence of a dead person. Just because a person is dead in this reality, doesn't mean they don't continue to exist in another. What I think people are seeing is the reenactment of an event or events that happened, and continues to happen through time. This is why what they see is partially transparent, because it is not completely in our plane of existence. In many cases the "ghost" does not interact with the person observing them. In fact, they are oblivious, because they are carrying out an event in their lives. There are sometimes non-living things in these ghostly scenes as well, such as trains. How can something that never lived be in ghostly form?