Nuff Sed, when God made Adam's body, it was not alive. He became a living soul once God had infused a spirit into into him. This means that the life of the body comes from that spirit. if it departs, the body must become lifeless and go back to dust. That's what death means. the life isn't there in the body anymore.
There is another kind of "death" in the Bible, which means the soul is separated from GOD. this is the result of sin/separation from God, and in Adam, it resulted in the fall of his own nature including his body and even the world. that's why illness, death and the like become possible and the world is permanently a place of suffering in general...Even after Jesus has come and ascended.
Nothing now works as it was designed to...not perfectly. So when we receive our bodies from our parents, we enter that fallen state and inherit Adam's lot of being separated from the divinity. This state of separation into we which we are all born is what we Catholics call "original sin". We start lives with spiritually dead souls. Upon conversion, its the soul that receives the life which was the gift lost by Adam by his disobedience when he failed the test just like the fallen angels before him. Yet because of Jesus, it is something we gain by a "new inheritance" through Jesus, the second Adam. And God himself comes to dwell in our souls as in a home. This is "justification", the thing you cannot earn, cannot merit, but must only receive. This live grows in you, slowly transforming you more and more (as long as you cooperate with grace) into what you were meant to be, into "another Christ". That's what we call "sanctification", it is a process. Glorification is the final union with God. all those represent how the life of God is planted in your soul like a seedling which if not trampled, will grow into a mature tree.
However, that new life born in the soul that makes the soul spiritually "alive", that reunites the soul with the divinity, that makes you an adopted child of God, does not redeem your body immediately, your body remains in its fallen state and in fact still suffers the full effects of the sin of Adam, suffering, pain in child birth, toil, illness, and finally death itself. the resurrection represents the redemption of the body as well, beyond the fallen body that suffers illness and mortality. The body is reborn almost like the soul was reborn first. Then the universe itself which is also fallen, is redeemed, and we have a new heaven and a new earth.
God never created this world to give it up, he made it for man and he made man to exist forever, with his full nature, not just his soul, and with his "world" the universe, that God had made for him. None of this was made to die/end. You face the dilemma of "why does Jesus come back" because you have a limited view or redemption. everything that was lost is to be returned, including our physical integrity and our universe as it was intended to be without suffering. All of that is the work of redemption, not just souls alone, but all of the creation made for human beings.
@Mya, as you know I'm catholic, so our beliefs here are NOT be identical with what protestants believe.
for us,
people who die in friendship with Jesus (this is what protestants may call "saved" though we have radically different beliefs about that too) will go straight to heaven if they have already been perfected while on earth, that is, fully purified of their fallen tendencies. Those who have still a ways to go will be purged first before going to heaven. However, both are those who have died "saved", if I can use that term. There's no more "choice" after death. once you die, the will's direction becomes permanent and unchangeable.
Those who die separated from God will go to Hell.
the mainline protestant view (not the SDA/JW/soul sleep one) does not involve a purificatory stage for those who die saved. They go straight to heaven, those who are not saved go to hell.
We also believe that at the resurrection, souls of both the just (saved) and the damned will be reunited with their reintegrated bodies
