Reincarnation: practical implications
Following up on my earlier post about the possibility of reincarnation (http://fakenous.net/?p=128): if persons are reincarnated, what are the ethical and prudential implications?
Debts
One person suggested that one might have an infinite amount of debt, accumulated from one's previous lifetimes (since at least sometimes, one fails to repay debts before one dies). However, I suspect that debts would not carry forward from one lifetime to another, given the lack of continuity (spatiotemporal or psychological) between lifetimes. The implicit understanding between two people, at the time they make a contract, is unlikely to include conditions constraining the actions of future incarnations that will have no memory of the agreement and probably no interaction with each other.
Punishment and reward
Likewise, you might have infinite positive or negative desert for your past good/bad deeds.
But perhaps there is a statute of limitations for good and bad deeds, such that rewards and punishments are limited to one's current lifetime. Or perhaps your degree of desert for a good/bad deed in your past diminishes as you get further in time from the deed.
Fear of death
One shouldn't fear death in the same way as one should if death is a permanent cessation of existence. One might still fear death, however, because one might fear that one's next lifetime will be worse than one's current one. You should have this fear if your current life is much better than the average life. (That is, the average life of a being that you could be incarnated as. It is unclear whether you could be reincarnated as a member of another species, and if so, whether it must be an intelligent species.)
Suicide
If your current life is much worse than the average life (of the sort of being you could be incarnated as), kill yourself. You'll probably wind up better off in your next life. (Note: Don't actually do this, because we don't actually know whether the reincarnation theory is true!)
If it is better than the average life, try to stay alive as long as possible. This is true even if your current welfare level is negative, as long as it is above the average.
Good news or bad news?
But how good is the average life? Probably not very good. Thus far in the history of the Earth, almost all people have been miserable. If you're reading this post, you are probably among a small percent of the richest, freest people who have ever lived on Earth.
Probably the pattern of misery repeats for intelligent species more generally, because this situation seems to be explained by very broad facts about nature. So if you can come back as a member of another intelligent species, things still don't look good.
It's even worse if you can come back as a member of a non-intelligent animal species. Then almost all of your lives should be as non-intelligent animals, since there are so many of them. And their lives are even worse than typical intelligent-being lives.
So reincarnation is likely bad news, not good news as it might at first appear. Probably your overall expected future utility is negative infinity.
But maybe not, because maybe intelligent species regularly discover cures for aging and then proceed to last for very long times, with large populations, at high welfare levels. So maybe the average welfare level of intelligent beings is very high. And maybe you are only ever incarnated as an intelligent being.
Animal ethics
If conscious beings can be reincarnated as members of different species, then the same beings who are now non-intelligent animals have been and will again be intelligent animals, and vice versa.
In that case, you are much more likely to next be incarnated as an animal on a factory farm than as another intelligent being. Perhaps a thousand times more likely. (The number of animals who will die on factory farms in the next 2 years is larger than the total number of humans in all of history.)
This makes the wrongness of animal abuse more clear than it already was.
An argument that it is metaphysically possible for you to be incarnated as a non-intelligent animal: we know that you were once a non-intelligent animal, because you were once a baby, and babies are non-intelligent animals. Also, you may again become non-intelligent (within this lifetime), because you may well become senile. If it's possible for you to be unintelligent at some stages of your life, then it's possible for you to be unintelligent throughout a lifetime.