Let's see what the scriptures say about the soul and death. (Psa 78:50) He leveled a path for His anger; He did not spare their soul from death, But gave over their life to the plague, (Psa 116:8) For You have rescued my soul from death, My eyes from tears, My feet from stumbling. (Psa 115:17) The dead do not praise the LORD, Nor do any who go down into silence; (Ecc 9:10) Whatever your hand finds to do, do it with your might, for there is no work or thought or knowledge or wisdom in Sheol, to which you are going.
It appears death is a type of sleep too. (Psa 13:3) Consider and answer me, O LORD my God; Enlighten my eyes, or I will sleep the sleep of death, (1Th 4:13) But we do not want you to be uninformed, brethren, about those who are asleep, so that you will not grieve as do the rest who have no hope. (Dan 12:2). "Many of those who sleep in the dust of the ground will awake, these to everlasting life, but the others to disgrace and everlasting contempt. (Act 7:60) And falling to his knees he cried out with a loud voice, "Lord, do not hold this sin against them." And when he had said this, he fell asleep.
Is it our bodies or soul that dwell in the grave? (Joh 5:28-29) Do not marvel at this, for an hour is coming when all who are in the tombs will hear his voice and come out, those who have done good to the resurrection of life, and those who have done evil to the resurrection of judgment.
Do we have immortal subsistence? (Job 10:5) 'Are Your days as the days of a mortal, Or Your years as man's years, (Isa 13:12) I will make mortal man scarcer than pure gold And mankind than the gold of Ophir. (1Co 15:53-55). For this perishable body must put on the imperishable, and this mortal body must put on immortality. When the perishable puts on the imperishable, and the mortal puts on immortality, then shall come to pass the saying that is written: "Death is swallowed up in victory." "O death, where is your victory? O death, where is your sting?" Psa 146:3 Do not trust in princes, In mortal man, in whom there is no salvation. And the telling verse is… (1Ti 6:16) who alone possesses immortality (God) and dwells in unapproachable light, whom no man has seen or can see. To Him be honor and eternal dominion! Amen. Immortality is what we receive from the tree of life (Jesus). (Rev 22:14) Blessed are those who wash their robes, so that they may have the right to the tree of life and that they may enter the city by the gates.
It's hard for me to accept ghost as being anything human. The bible speaks of the total opposite!
Now as for evil spirits pretending to be human souls, that may be the real question?