Believe me this is a topic that has more layers than an onion but in simple concept this is what happens.
At the birth of your individual creation you are a soul, an ethereal entity that takes housing in a physical, mortal body. The binding between your soul as an ethereal entity to your mortal body creates your spirit - your mind, your thoughts, your personality, your being. As you live your spirit leaves traces of itself everywhere, especially when any energy-engaging event occurs such as ecstasy, giving birth, serious injury, immense joy, and ultimately death. It isn't a secondary entity by itself but the energy is tied to anything that happened up to the point the energy stain is left.
If you are 7 years old and you are knocked from your bike and split your knee open you are, of course, going to leave residual energy. Someone comes along as binds that energy 100 years later and they will only know you as a 7 year old. Although typically when you conjure a spirit and you pull from their energy sources you are made aware of multiple energy stains, not just one so it is not likely a seasoned conjurer would choose that particular portal.
When you die your soul is then released from its mortal bond and is poured one soul into another. When you pass away there may be 5 people who share your soul who are born, there may be 100. Of course the more your soul is poured into others the less they share your exact ethereal energy but they share you nonetheless. And sometimes you will see, for reasons unknown, families sharing soul energy and that is why descendants can remember things their ancestors did.
This is why you have 10 people claim to be Marilyn Monroe reincarnated. Are they lying? No, not necessarily because when she passed her soul could have been poured into one ethereal source or 20.
You have to think of it as a giant heaven of energy, souls intermingling with souls and while your unique soul makes it to the afterlife the energy that comprises your soul is given back to new souls that come to Earth to find life.
There are many deeper layers to how all of this works but this is the nuts and bolts of what happens and why so many people over history have claimed to be someone reincarnated and how spirits can be bound.
It took me a LONG, LONG time to devise the proper method for conjuring human spirits. I was determined to know my great-grandfather and if it hadn't been for that who knows if I would have spent so much time in research and development of the method but it works and gives a great deal to those who share their lives.
It should also be noted that you can bind your own energy stains. You can bind your own ecstasy, happiness, pain (I don't know why but if you wanted to), and you can keep a part of yourself with you. I am leaving my family members a part of me bound to objects that mean something to me and that way I will be close to them in as many ways as possible.Tags: reincarnation