As far as I understand it, reincarnation is such a difficult concept to grasp, because we all live under the impression, that we are fundamentally separated from the world around us. But how separated are we really?
We need water and food to survive, we need shelter, we need other people to communicate with and we need them as much as they need us. We've gotten used to so many benefits of Western civilization: clothing, food, housing, clean water, safety.... but you wear clothes, that were produced by somebody else and even if you did weave them yourself, you still had to purchase the wool. And even if you had sheep at your house, you didn't produce the grass that they fed on.
Reincarnation does not postulate the existence of a soul or an eternal non-changing entity. It rather describes consciousness as a stream without beginning or end, which is constantly changing and evolving over time. So why are Buddhists so sure that there is no end to it?
Again this brings us back to the first chapter. We see ourselves as a being - a human being. Each one of us was given a name. You could say we see ourselves as a phenomenon. We have a birthday, an identity, a passport, an address, a face, a fingerprint, a character. When we see a grazing cow, we don't see that identity. To us it is just a cow, completely different from us in every aspect. A different body, different behavior, no real character, no face, no address, no passport, no identity.
When we look a little closer, this cow's consciousness, or any other being's consciousness for that matter carries similar qualities to ours. It feels pain, it avoids pain wherever it can, it likes to sleep in and doesn't want to be woken up. So why do we eat cows but refrain from eating our neighbor, even though he's a lot more annoying than the cow?
Because we are blind to reality. We are not separated from the beings around us, we are deeply connected with them and this is something that we can actually experience, not only during meditation but by practicing compassion towards them. This is the key to understanding reincarnation.
In Buddhism there is no "self". The "I" is constructed out of so many layers and influences.... education, habits, behavior, feedback, upbringing, environment....It is a great illusion to believe in a seperate unchanging identity, because from one second to the next, even the cells in your body disintegrate and die. Second by second you are changing and the physical person you were just a minute ago, is already dead. Your mind-stream has changed as well and is still changing while you're reading this sentence. You are neither your dying body, nor your changing thoughts. However we can agree that you "are". But this thing that "is", would you say that it is alive? Is it dead? Can it die?
"Life" is a concept and according to this concept you have never lived. Life implies that a clear distinction can be made between "living" and "dead", when in fact there is only one category: "consciousness". Not for a single second have we truly been "unconscious" and that's why ultimately we cannot die. Not the way that we think, because we have never lived as a separate being, but instead as a drop in the ocean of consciousness. All our bodies will decay, our passports will be out of date, our address' will change and one day we won't have a fingerprint anymore, because all that's left of our right hand is a pile of bones. But not for a single second will we be isolated from the consciousness around us.
You already are that cow on the grass. You already are that annoying neighbor, you already are the fly in front of your window trying to get out, you are your family, you are your kids, you are so much more than you think you are. You are the spider in your room, you are the homeless guy on the street, you are the clerk at the supermarket. You are, because of your consciousness and the consciousness of a billion other beings are entwined.
But we forgot all that. It kind of comes back to us, when we help them. I think that's why we feel good about doing good things to others, why we ultimately get zero satisfaction from causing damage to them. This is the root cause of karma and why we have to suffer the consequences of all our actions. This is why many Buddhists put so much emphasis on compassion. Because there is only a very superficial difference between us, but a much larger portion that holds us together pretty tight.
When you think about it, this is all so normal and almost boring. It's funny that this concept is understood as a metaphysical, crazy "New-Age" belief by so many people. In fact I heard many Buddhists say that they only go along with the "logical stuff" of Buddhism and not the "religious stuff like reincarnation".
Really makes you think.