What are the rules of reincarnation? I have seen this question asked, and it is a good one. It may be thought that it is one that cannot be answered except by appeal to religion or philosophy, but actually over the last 50 years of research we have begun to see the outline of how reincarnation seems to work. What I will say here is on the basis of the study of solved past-life memory cases, those in which the previous person has been identified and in which we can have some high degree of confidence.
The most general thing the cases have brought us to understand is that reincarnation is basically a psychological process without any cosmic “rules.” It is not lawful in that way and does not seem to be governed by any processes other than psychological ones. That means that many things about it vary a great deal, from person to person and from culture to culture. We have many indications, from different lines of data, that suggest that we can have a good deal of control over when, where and in what families we reincarnate. We do not see that in all cases, but we see it often enough to justify saying that.
In the great majority of cases, the reincarnation is close to where a person died, or at least within the same country or culture. Reincarnation can be in a different country, though, and when that happens, there is usually a reason of some sort for it. The time between lives also varies a lot, and can be very short, from immediate, to hundreds of years. We do not yet understand all the factors that relate to the length of the intermission between lives, but we do see shorter intermissions when people die very young or violently.
One may change sex between lives, but this is something that varies a lot by culture, and in places that deny that it can happen, we do not find cases (perhaps because they are suppressed, but there really do seem to be fewer of them in those places).
In many cases there are birthmarks or other physical signs linking people in two different lives, but these are not invariably present, and appear to have a psychological basis too. That is, whether or not they appear seems to depend on the meaningfulness of these things to the previous person, who then somehow transfers them to his new body in the process of reincarnation.
It is the same with behaviors, including phobias and skills. When cases are solved, children with past-life memories behave toward people known to the previous persons in ways appropriate to that person. The child may have phobias that can be related to the manner in which that person died and when there was a violent death (such as a murder) may display other signs of post-traumatic stress disorder. The child may also possess skills, including language and handwriting skills, possessed by the previous person, and when these appear they too are things of importance to the previous person.
Thus, although we can discern no fast “rules” that govern how reincarnation occurs, we can see some clear patterns. These patterns include cultural variations, which I will write about elsewhere, but all point toward reincarnation being an individual, psychological process that is not governed by any natural law and is not the same for everyone.