I wonder how much real biblical teaching on human nature is given in churches. What is taught is often Greek dualism (with soul and body being two distinct kinds of existence) usually seen through the thought of René Descartes. Sometimes it is tripartism (spirit, soul, body).
Both these views are untenable if one takes seriously both scripture and science. In Hebrew and modern thought human beings are a psychosomatic unity which can described in various terms: mind/body, soul/flesh, spirit/soul/body, heart/appearance, outward/inward etc.
It is possible for Spirit and Flesh to be separated and the saints in Paradise and the spirits in Hades are in that strange position. But this is not natural or normal – it is the result of the catastrophe of death. Without bodies we exist only as shadows or resting souls.
But what is “Spirit”. In Genesis it is the breath of God which He lends us for life and takes back to Himself in death. Often, it is best translated as “mind” or “energy” or just “life”. But “spirit” has no substance or definition. It can only exist either as a function of a human nervous system or as something preserved in God’s memory and by His will.
Brain Science is showing us that many of the traditional characteristics of the soul are connected with our brains so intimately that there is no real dividing line between body and soul. There is simply personality.
Personality is responsible to God and is made in His image. The very concept of personality was worked out by Christians trying to describe the Triune God revealed in scripture and their experience. The living trinity is One God subsisting in three persons. You are one flesh subsisting in one person. The “spirits of just men made perfect” in heaven are personalities waiting for their new substance, the “Spiritual” body which will be material but not “flesh” in the sense of being naturally resistant to the desires of the spirit.
In Cartesian and Greek thought the soul is immortal in itself. It is a substance yet radically different from earthly substance.
Modern life sciences are undermining this picture. If we define human personality as an immaterial soul residing temporarily in a bodily shell then we will feel threatened by the more materialistic view of both consciousness and personality emerging from the structure of our bodies.
If we see things biblically we should be grateful that naturalistic philosophy is catching up with revealed reality.