In 1920, Thomas Edison announced work on a machine via which the spirits of the dead could communicate with the living. He succeeded. Nineteen years later, the technology had advanced sufficiently for the New York World's Fair to exhibit the world's first proper Séance Engine,
an automaton designed to channel a ghost as its control mechanism, serving as a prosthetic device by means of which the ghost could interact with the physical world.
Normally, there is no afterlife*. The dead are dormant, not experiencing consciousness since their original death. Unless something in the mortal world wakes them up, in which case they can use the Séance Engine summoning them as a body**.
Now this leaves all kinds of interesting ideas to play with. Everyone who ever died or who knows they're eventually going to die and wants to be prepared is going to want a prosthetic body. Who makes them? How long until sweatshop owners come up with the idea of renting them? How does society work when nobody
permanently dies, the closest you could come being for all the living to forget someone's existence therefore preventing anyone from wanting to summon them, or summoning them yourself and keeping their new mechanical body permanently imprisoned so they can't be summoned into a different one outside of your control, etc.
* Several religions claim Séance Engines remove all memories of the afterlife when they drag someone's soul back into the mortal world or that the things summoned up by Séance Engines aren't what they claim to be, etc.
** The initial prototype was basically just a telegraph. The ghost could send and receive rudimentary signals. Later, more sophisticated versions were more along the lines of mechanical bodies.
Again assuming that people tell the truth although its more likely here.
