I wish to offer a couple of ideas to consider in regards to whether Humans have eternal spirits. These may have been mentioned in earlier posts in some way or another.
I say spirit because it is generally believed as being the part of us that survives death and enters Heaven. While the 'soul' seems to be attributed as being the same in some cases, biblically, the soul seems to be described as either the life-force breathed into us by God or what we become when our flesh has life breathed into it. "And man became a living soul..." The soul being anything else is not a biblical concept.
The first idea I want to discuss is the belief that living Humans do not currently possess immortal spirits. As I mentioned above, according to the Bible, we became living 'souls' by the joining of our bodies and life-force. But there are places in the Bible that suggest our soul is actually the God-breathed life-force itself. Animals also possess this life-force. And when we die, the flesh returns to dust and the soul returns to God whom gave it.
So from this, one may assume that when we die, we are simply gone, not conscious. Not aware of anything at all. A Million years could pass but from the moment we close our eyes in death to the moment we are raised again, it will be an instant. The dead in their graves now may be just that, dead in their graves. All they are is there, within their coffins. The dead know nothing. And we do not survive death.
But then the Bible also speaks of a resurrection of the dead. However if we cease to be upon death, then how are we presented with a new, spiritual body at this resurrection? The Bible states this spiritual body is new, not like the old one. It also describes the original body as being like a seed, which must be buried in the earth so that the flower can exist. The flower being our eternal state which we receive at the resurrection. But where and in what form are we in order to be given a new body to enter? Our brains will be dust, all our memories, thoughts and feelings seemingly gone...
There are theories regarding 'paradise' and 'sheol', that try to explain where we exist in the meantime, in between death and the resurrection, but these suggest that we must have some form of aspect within us now that survives death to end up in such a place.
The other idea assumes we indeed do have a spiritual component within us now. And revolves around the idea that the brain is simply a tool we make use of, a way to manifest our will in the World. Each area of the brain has it's own function, and without that area of the brain, we are denied that particular function and the subsequent abilities it allows, yet we are still 'us'. It is like trying to type a sentence that requires the use of the 'A' key yet it is broken or missing. We still desire to form our sentence yet we are unable. We are the puppeteer while the brain is the strings. Without the strings, we cannot move the puppet.
So we may literally be controlling our own avatars. Our will is made manifest through the use of physical organs and limbs. Our invisible selves are housed in the physical machine and we can articulate ourselves through the manipulation of the machine.
Remove the brain and 'you' will still exist, however, you will not be able to manifest your will or your personality in the physical World. Each of us may be a spirit inhabiting a body. The brain may not be the controller, but the controls. The receiver, not the signal. This would make diseases like dementia all the more horrifying, knowing that our loved one is trapped within their body, unable to function correctly. But does this fit with the Bible? Ultimately, any theory that is to be taken seriously must fit with the only source of information we have regarding any of this in the first place, the Bible!
At the same time, if we end up denying that we have a spirit within us now that survives death and makes us who we are as individuals, yet accept that the Bible is true, we must provide an explanation for a few stories in the Bible itself:
If Humans possessing eternal spirits in life is in fact not biblical and we are gone when we die then what happened between Saul and the Witch of Endor? From where did the spirit of Samuel come from? The witch screamed in fear suggesting she did not expect her ritual to actually work... Perhaps God intervened? If so then all we can do is speculate on what He did.
And if the dead are gone, how did Moses and Elijah appear to Christ? In what state did they appear? Resurrected? Are our eternal, resurrected bodies able to appear anywhere throughout time and space? Being eternal would suggest they are not limited by either... In that case, would it not be possible that our future, resurrected selves can view us sitting at our computers now? Highly unlikely it works this way but it makes you think...
If men are gone when dead until the resurrection, how did the thief get admitted into paradise that Day? Is paradise a different place to Heaven? Does this mean Christ entered paradise upon His death too? Is this where Abraham and the poor man were/are?
*In regards to the case of Lazarus, it is clear that he was not resurrected in the end of days sense, but simply brought back to life. His life-force was breathed back into his body and he returned to a living state, however he would only go on to die again later. Like the Godly men who came back to life upon Christ's death on the cross. This is different from being raised into a new, spiritual body in the Resurrection because the Bible states that Christ was the first to be resurrected into this new body. However, where was Lazarus between his death and his being brought back to life? When I say where was he, I do not mean his physical body, as that was laying there dead, I mean his actual self.
The Bible seems to swap back and forth between mankind having an eternal spirit which survives death (The tale of the rich and poor man, Samuel's seance etc.) and mankind being no more upon death (Ecclesiastes).