The spirit is the secret, by which man is alive, acts, sees, hears, moves, learns and works, if the soul leaves the body partially, most human body’s systems stop and only few ones continue working to keep his life like the heart and respiratory system, this happens when man is asleep, but if the soul leaves the body totally, all human body’s systems stop and man dies.
In spite of this great importance of the spirit, modern technology, scientists, wise people, philosophers and others are unable to realize the fact of the spirit and even its place in the human body.
We can say that the spirit is from abstract divine facts that we can realize its effects but we can’t realize its real being. As man is alive and can move then this is the evidence that the soul is inside him, when his systems and organs stop working and he can’t move then this means that his spirit left, but what does it look like? What is its nature? And where is it in the human body? This is only known by its creator, so the Koran says:
“They ask you concerning the Spirit (of inspiration). Say: "The Spirit (comes) by command of my Lord: of knowledge it is only a little that is communicated to you, (O men!)" Surat Al-Israa’, Verse 85.
We can see examples of the spirit from tangible life and our invisible world too. In tangible life we see the effect of electricity when we run machines or light the bulbs but no one can see electricity itself. In invisible or abstract world we see the effect of love and hatred in people’s behaviors but we can’t see them actually.
Then the spirit is a hidden secret that means life to man as this secret is from God, He says:
“And breathed into him of My spirit,”
Surat Saad, Verse 72.
So it is a luminous fact not seen by apparent organs or tangible machines, imam Abul-Aza’em says about this: (The spirit is the picture of its Lord and its innovator, how can my body recognize it? If higher angels see its lights, they will fall prostrating for it longing for my grants. If the spirit appears when it is clear to the universe for a breath, it can hide it by its luminosity.)