In Genesis 2:7, we read, "And the Lord formed man of the dust of the ground and breathed into his nostrils the breath of life, and man became a living soul."
In Mark 8:36, Jesus said, "For what shall it profit a man if he shall gain the whole world and lose his own soul?"
In Matthew 10:28, Jesus said, "And fear not them who kill the body, but are not able to kill the soul, but rather, fear him who is able to destroy both the soul and the body in hell."
In 1st Corinthians 15:44, Paul said, "It is sown a natural body, it is raised a spiritual body. There is a natural body, and there is a spiritual body."
In 2nd Corinthians 4:16, we read again, "For what cause we faint not, but though our outward man perish, yet the inward man is renewed day by day."
From these authoritative biblical sources, we know without question that the soul exists, and it is the spiritual dimension of man/woman. It has been known from antiquity that man/woman is, and has always been two persons in one: the body and the soul.
Although inseparable during the course of our lives, the two are different from one another. The body is made of blood and flesh and interacts with the physical world. The soul is made of the spirit and interacts with the spiritual world.
It is through the soul that God, being a spirit, interacts directly with humankind. The soul is also the entrance through which Satan and his demonic agents get access to the body. In other words, the soul is the doorway through which good or evil deeds are given physical expression by the body.
Consequently, when the physical person turns away from the word of God and engages in harmful and depraved behaviors, those deeds transform his soul into an inhospitable dwelling for the Holy Spirit, and the Holy Spirit would depart from his soul.
When this happens, Satan immediately sends thousands of his demonic agents to occupy the corrupted soul to entrench those depraved behaviors, making the corrupted soul receptive to evil thoughts, sexual immorality, theft, murder, adultery, greed, malice, deceit, lewdness, envy, slender, arrogance and folly.
With these vices comes the degeneration of the soul as it feeds on the lies and false doctrine of Satan. Thus corrupted, the soul would drift away from all things righteous, and know only evil as the means to express itself.