Supernatural nature of mortalism

To accept the belief system of mortalism one has to accept at one point or another some supernatural controlling factors. Mortilism is defined in this discussion as the belief that a specific ixperiencitness is connected to one specific body and once that body no longer produces any consciousness that ixperiencitness will never be produced again. Stated in another way, once your body is permanently dead, it will never produce a consciousness that you will experience ever again nor will any other consciousness producing body.

If you eliminate one by one the reasons that natural causes will not necessarily permanently destroy an ixperiencitness you are left with an unknown natural cause or causes or you have to postulate a supernatural cause for the permanent elimination of all ixperiencitnesses at the death of the body that produced it in the first place. What is the mortalists cause or causes for the permanent extinction of ixperiencitness at death? Should a reasonable person accept the mortalists assumption without proof? Superimmortalism accepts, along with mortalism, that there comes a time where a consciousness producing body no longer will or can produce a consciousness with a specific ixperiencitness. What it does not accept is that another body can not produce the same ixperiencitness. It not fair to say that you can not prove a negative, the negative being prove that an ixperiencitness that has existed before can not show up or be produced in another body.