The relationship between the body and the soul is complex and ultimately a mystery. The importance of this relationship, however, is necessary to grasp because by doing so we will have an insightful understanding of ourselves and the way God made us.
So how does the soul and the body define us as human beings? How does the relationship work between the soul and the body in order to come together and form an individual human being made in the image and likeness of God? How can we describe such a relationship? Here are a few ideas that exist that attempt to answer these questions.
1. WE ARE BODIES WITH SOULS
This is a very common belief; in fact it is a belief that is oftentimes assumed without reflection, that we human beings are bodies that have a soul in it. The soul is simply present in ourselves, just like a seed is simply present within an apple. Sure the soul is important for the existence of life, but it is not necessarily part of us, it is merely within us.
Such a view is understandable because unlike our bodies we cannot see our souls, so it is very easy to talk about it in a distant sort of way. Nonetheless, it is incorrect to say that we are bodies with souls. Our bodies after all have no life without the soul. The soul is not just important for life, it is a sine qua non, a foundation for life without which it would be impossible to live. Adam was not alive, and thus was not Adam, until God breathed into him the soul (Genesis 2: 7). Therefore, something that is deeply connected to the existence of life cannot merely be something that is within us; it must be a part of us.
2. WE ARE SOULS WITH BODIES
This is also a common view--that we are in fact a soul with a body, as if to say our defining nature as a human being is our soul and the body merely encases the soul. Such a view is also understandable because, as described above, it is the soul that gives us life and is essential for life. Also after death our souls go to Heaven, and it is assumed that we will be aware of our presence when we arrive there. As a result it seems clear that our identity is rooted in the existence of our soul.
This, however, is also not fully accurate. For one, just as the soul is essential for life, so is the body essential for life. In Genesis 2: 7 God made sure to have a body first before breathing a soul into it. Thus the body seems to be equally as important for a human being to have life as the soul and thus equally necessary for human identity.
Also, that the soul after death proceeds into Heaven actually defeats the idea that we are souls with bodies, because in order for such an act to happen we must first die. And death was never supposed to happen in the first place, according to God’s original plan. Thus when death, the separation of the soul and the body, occurs it disrupts the way God originally made us and thus disrupts our true and original identity. We may very well have conscious thought and experiences after death and be alive in the sense of attain eternal life with God, but that does not change the fact that we are not a person; we are not our perfect and complete selves. We are dead in a way that God never intended us to be.
Proceeding from that, the idea that we are souls that simply have bodies leaves a big question open: why have the bodily resurrection of all people in the Final Judgement? If we really are merely souls with bodies then why not just let our souls be present with the Lord in Heaven? Why put us back in our original state? The ‘souls with bodies’ idea cannot answer such a question.
3. WE ARE BODY-SOULS
We do not really HAVE a body, nor do we really HAVE a soul. We ARE a body AND a soul. The way that God intended us to be and originally made us to be was for both body and soul to be united. This is the only explanation that fully accounts for what we see in Genesis 2: 7 and for our encounter of death and the afterlife. Though we will experience the Beatific Vision and God’s glory upon entering Heaven we are still incomplete without both body and soul being united.
This further explains the importance of the Final Resurrection. With our bodies and souls being reunited at the end of time we will be able to worship and praise God in the original state that He made us in, thus making it God’s final victory over evil by conquering Original Sin itself. This unification, then, is rooted directly into God's Original Justice and, as a result, into our identity as followers of Christ.
We are, therefore, not bodies with souls nor are we souls with bodies. We are body-souls. It is in this deep union between the two that we find our essence as human beings.