I have always believed in reincarnation - that souls come back to the earth to be reborn into new bodies until they reach a state of near-perfection when they can choose to "retire" from life or continue to return to help others (i.e. Mother Teresa).
Reincarnation is the only philosophy that makes sense to me and my own heart and mind can't offer faith without fairness. Without reincarnation, life is the luck of the draw, a giant spin of the cosmic roulette wheel.
Landing on black is the beautiful, intelligent child of loving parents and comfortable means. College, marriage, children, an abundance of material things.
Landing on red is the brutalized slum child, fighting for daily survival - an uncaring alcoholic mother, a non-existent father - ending in prostitution, drugs, prison.
Sorry, it was the luck of the draw? Nope, I don't buy it. If there is a superior being, of whose plan we are all a part, I have to believe that roulette wheels are not how he/she makes decisions and that there is more to it than those relatively short, wildly disparate existences.
There has to be a more level playing field for learning and therefore, an equal opportunity to be judged by what we learn. I believe as we are born and re-born, we review and reflect on our actions here on earth. We deliberately put ourselves into incarnations that will help us with the areas in which we were weak to gain empathy for those to whom we were cruel or superior or un-generous.
From one existence to another, we will be male and female, black and white, gay and straight, rich and poor, strong and weak, until we have run the gauntlet of human experience.
Karma is a trendy term right now (and is, of course, the root of "what goes around, comes around") but many people confuse karma with punishment. Karma isn't punishment but self-appointed opportunity to learn from our mistakes. Like some obstinate students, we may require repeating a class more than once before we can pass the test and move on to a higher grade.
Mostly I am optimistic that we are all on a slightly upward-inclining evolutionary path although there are certainly days when I despair and then I try to tell myself that God-time isn't the same as ours. If it takes vast millenniums for us to reach the end of our spiritual journeys, so be it. Our only concern now should be how we are handling our present existence.
I don't believe progress depends on denomination, which no doubt also changes from life to life. The same learning curve is expected of Christians, Jews, Buddhists, Muslims and Pagans. None of the great, or even minor religions, have a monopoly on either kindness or cruelty.
It is popular to say that God created us in his image but I believe it's just the opposite - we created God in our image and therefore, made him far, far too small in order to suit our self-focused prejudices.
There is a huge body of research about reincarnation and age regression should anyone care to read it. It is at least as "proven" as any other philosophy. But I have no interest in converting anyone. People have the belief system that meets their particular needs and it doesn't really matter except for the harm we often cause by our insistence in digging the mote out of our neighbor's eye rather than extracting the log from of our own.