Response from reddit
The following reply was posted on reddit by
omfalos
The best argument for reincarnation is that anything that can happen once can happen again. I believe in reincarnation, but the version of reincarnation I believe in is pantheistic and highly randomized. If I reincarnate, it will be as a strange alien creature many trillions of years in future. Reincarnating twice within the same universe should be unlikely, let alone within the same species.
It is assumed that your conscious experience is linked to a time-irreversible collapse of the wavefunction. What you do in a future life isn't allowed to affect a past-life in any way.
You cannot reincarnate anywhere in your past light-cone.
If you reincarnate to another planet it will be a time where light from that planet cannot reach your planet until the time where you died. The path light takes in the universe will be determined by General Relativity, thus if you find yourself in a black hole where your consciousness will have a hard time escaping since all future timelines point to the singularity.
You can only reincarnate into a future lightcone. Thus your conscious experience now must be the continuation of a conscious experience in your past lightcone. This can be explained by your consciousness being tied to a particular quantum wavefunction. Thus the collapse of the wavefunction must be linked to a specific collapse of the wavefunction of the past lightcone resulting in the continuation of your conscious experience.
If consciousness is the manifestation of a quantum system, that to me suggests solipsism. A quantum system can potentially be very large, encompassing multiple people. Either everybody has overlapping quantum systems, or there is one large quantum system that happens to be centered on a particular human brain.
It follows logically that there is a nonzero probability that you end up reincarnating even though your body didn't actually die, the probability for this is greater with solution2 since there isn't any time delay.
If you were to switch body you may not actually notice it since you may end up only with the memories of your new body and thus you wouldn't be able to tell you only have controlled your current body for a year.
Even if memory preservation would be required for reincarnation a body switch could still occur due to 2 brains having very similar memories, then you would experience a memory continuation even though your brain is now different. The memory continuation may not be perfect but you would not notice that since there wouldn't be any actual transfer of memories.
Since you wouldn't notice your consciousness having switched location you wouldn't notice if your consciousness was constantly switching location. Therefore it cannot currently be ruled out that there is really only a single consciousness in the entire universe but you do not have memories of your conscious experiences in the other bodies since these memories are left in the brains you currently do not have any conscious experiences in.
If consciousness can jump across the universe into another body, or island-hop across Boltzmann brains, then that opens up a lot of possibilities. I will try to use the analogy of a slide projector to describe increasing degrees of freedom in the way consciousness can jump across time and space.
1. Slide projector with slides in sequential order
Moments of experience are cut up into slides and fed into the projector in sequential order. The laws of physics govern the order in which slides are fed into the projector. Each slide contains a memory that links it to the previous slide.
2. Slide projector with slides in random order
The slides are now out of order and the projector cycles through slides randomly. The slides are still nevertheless experienced in sequential order, because each slide contains a memory that links it to another. Memory sustains the illusion of sequence where none exists.
3. Overhead projector with room for multiple slides
There is an overhead projector with a surface that can hold multiple slides. The surface is very large and projects every slide at once. The slides are still experienced in sequential order because each slide contains a memory that links it to another. Memory sustains the illusion of time even when every experience exists simultaneously.
4. There is no projector
There are no laws governing which slides are projected or in what order. Every experience is a prime mover that pulls itself up by its bootstraps from nonexistence. Experiences are self-caused with no physical chain of causality. The governing principle of the universe is Murphy's Law: every experience that can exist, does exist.
This final version dispenses with the problem of overlapping quantum systems. Each conscious experience is a universe unto itself outside which nothing exists. My belief is that there are an infinite number of conscious experiences arranged in one long sequence. The sequence cycles through every person's life one-at-a-time, with alien lives mixed in for good measure.