Humans were created in the image and likeness of God, a tri-partite being. Man's spirit is eternal. He was created to eternally be in fellowship with God. A person CANNOT cease consciousness, no matter how much a person may want to. (Body yes, but spirit...no)
It is man's spirit that is in God's image. Man's body was formed from the dust, but his spirit (or inner man) was breathed into him by God. Genesis 2:7 says: "And the LORD God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living soul". From this verse we have the picture of Adam's lifeless body being formed from the dust, God breathing life into his nostrils, and the body then coming to life.
DEATH DESCRIBED
When we die our spirit leaves our body. James 2:26 says "For as the body without the spirit is dead, so faith without works is dead also." The spirit does not go out of existence when it is separated from the body in death, but returns to God who gave it Ecclesiastes 12:7 says; "Then shall the dust (body) return to the earth as it was: and the spirit (life) shall return unto God who gave it." This verse not only defines death as the separation of the body from the spirit, but it also shows that man's spirit is eternal , it does not go out of existence at death, but returns to God.
Notice also the description of Rachel's death. "And it came to pass, as her soul was in departing, (for she died) that she called his name Benoni: but his father called him Benjamin." --- Genesis 35:18 Jehovah's Witnesses teach that there is no difference between the soul and body, They claim that both are mortal and go into the grave together. The description of Rachel's death however clearly shows that the soul and body are not the same thing. Rachel's body was lifeless, but at death her soul left her body.
The death the widow of Zarephath.'s son and his revival gives further insight into the soul of man. This young man was raised miraculously from the dead by Elijah. 1 Kings 17:21-22 describes this miracle. "And he stretched himself upon the child three times, and cried unto the LORD, and said, O LORD my God, I pray thee, let this child's soul come into him again. {22} And the LORD heard the voice of Elijah; and the soul of the child came into him again, and he revived."
We notice here that it was the same soul that left him at death and returned to him at revival. His soul therefore did not go out of existence. The person that Elijah resurrected from the dead was the same person that was alive before death. It was not another soul that was given to the lifeless body, but the same one as was conceived in the widows womb through the union of her and her husband. If the soul became extinct at his death, this would be impossible.
PEOPLE ARE STILL "ALIVE" AFTER DEATH
This may seem like a contradiction in terms, yet the Lord Himself plainly explains that Abraham, Isaac and Jacob were still alive even though they were dead. He said "And as touching the dead, that they rise: have ye not read in the book of Moses, how in the bush God spake unto him, saying, I am the God of Abraham, and the God of Isaac, and the God of Jacob? {27} He is not the God of the dead, but the God of the living: ye therefore do greatly err." --- Mark 12:26-27. This was the Lord's answer to the Saducees who did not believe in life after death. What plainer proof could be given for the immortality of the soul than these verses. Abraham, Isaac and Jacob were all dead (in their graves) when Jehovah declared Himself to be their God. Although they were departed from this world, their spirits continued to live. Jehovah could not be the God of extinct persons.
The Lord also taught the immortality of the human soul in Matthew 10:28 --- "And fear not them which kill the body, but are not able to kill the soul: but rather fear him which is able to destroy both soul and body in hell." Tertallion, an ancient writer rightly said of this verse "Here we have recognition of the natural immortality of the soul, which cannot be killed by men"