Christians believe in the resurrection of the body. This means that in some sort of way, at the last day, we will have a ‘resurrection body’. What does this mean and how can this be? Is God going to gather up every last particle of me and put me back together again? What about the people who were blown to bits by bombs? What about those who drowned and were eaten by fish? What about those whose bodies were eaten by lions and tigers and bears? Oh. My.

We have to think of our resurrection body as part of our body that we have right now. Think of it this way: in my downstairs bathroom I have a picture of myself when I was two years old. I look pudgy and ponderous. Then there is a picture of me when I was eighteen and graduating from high school. I look handsome and hopeful. Then there is a picture of me a few years ago looking well, pudgy and ponderous again. Each photograph was me, and yet the physical me in each photograph is completely different. How could that baby me, that young man me and that middle aged man all be me? 
Indeed, the biologists tell us that our bodies renew every cell every seven years. In a way, every seven years I get a different body, and that is what the photographic evidence tells me too. Therefore, this body that I think is so physical and so permanent and so solid, is really very ephemeral and transitory. It’s always changing. Nevertheless, there is also a part of me that is continuous with all the different bodies I have inhabited. That’s what we think of as the soul. 
But where is the soul? It is not in my body like water in a jug, it is more in my body like water in a sponge. I am an ensouled body. My soul is in every part of me. My soul is not in my brain or my heart or my blood vessels or my big toe. My soul is in every cell. My body and my soul are intermingled. Therefore, what is this resurrection body? It is the soul that is in every cell of me and it is arguable that the soul is incomplete without each cell. This cell soul is my resurrection body. It is the soul of me in every part of me which will one day be resurrected. That is what lasts forever, not the very physical stuff of me.
But this makes it sound like the soul part of me is somehow less physical. Like it is the ghostly part of me. The exact opposite is true. It is the soul body part of me that is the most ‘physical’ at least it is the part of me which is most ‘real’ because it is the part of me that transcends the different physical manifestations that you can see in those pictures. It not only transcends them, but it will last forever because that is the eternal part of me.
Now I say all that to say this:  when you have this concept of the resurrection of the body, then suddenly re-incarnation doesn’t make any sense. What, am I to suddenly adopt another physical body altogether? What about the fusion of my soul and my body that existed before? So it wasn’t a real fusion after all. It really was the fact that my body was just the container for my soul. No. We reject this idea. The Judeo Christian view is that the soul is engrafted and is inseparable from the body (at least from the ‘soul body’ I have been theorizing about)
Why does it matter? It matters because matter matters. In other words, it matters because we believe the body is important. We believe the physical world is important. We’re not gnostics who believe that the physical world is irrelevant and the only thing that matters is the spiritual realm. No, we believe that everybody matters because every body matters. What I do with my body immediately affects my soul. What I do with other peoples’ bodies affects their soul and my soul. What I do with material things affects my soul and other people souls because our souls and our bodies, the spiritual and the physical are all wrapped up together.
This integration of the soul and body is totally necessary to have a Catholic, a sacramental and even a Christian philosophy. Re-incarnation, on the other hand, simply considers the body to be a container for the soul. Do you see how this affects everything? If the body is simply the container for the soul, it doesn’t really matter what you do with the body. See how it impacts morality? It doesn’t matter what you do with your body or another person’s body sexually because the body doesn’t matter. See how it affects the pro life debate? If the fetal body does not yet have a soul (a view that re-incarnation can well support) then it doesn’t matter if we kill it.
Finally, some will say, “Well, we can’t know one way or another. Resurrection of the body might be true. Re incarnation might be true. I guess it’s a toss up.”
No it’s not. We have a historical occurrence of resurrection. Jesus Christ rose from the dead. People saw him. They were scared. They touched him and had breakfast with him. Those who claim re-incarnation have nothing more than subjective experience and a theory.