The problem is in grasping the non-dualistic or Advaitic truth. The soul,which is present in the form of consciousness is not limited to the individual, but it pervades all the three states as its formless substance and witness. Because one limits the soul or consciousness to the individual physical entity, he will not be able to grasp the ultimate truth or Brahman.
The soul is in the form of consciousness. If the consciousness is there then the body and the world are present. The consciousness can exist with or without the body and the world. The body and the world are dependent on the consciousness for their existence. Thus the body and the world are mere mental, thus they are not real. One limits the consciousness the innermost self to the physical entity, he will remain thinking, and the soul carries on in some individual form to reincarnate.
When the body and the world are made of consciousness, there is no second thing other than consciousness (soul or Atman), hence it is nondual. The body and the world are reality only on the standpoint of the false self (‘ego or waking entity’), within the false experience (waking). In reality, nothing exists other than the consciousness, which is the soul or consciousness. When the body, ego and the world are made of the same stuff than the division within the consciousness is mere illusion. The one which is in ignorance and that one which is aware is consciousness. When self is in ignorance it experiences the illusory waking experience as reality. When it is aware of itself then there is no illusion.
There is neither the world nor its contents , because the diversity or duality is mere mirage .And mirage has no value in reality, thus nothing exists other than oneness. Just go on and on in thinking process, it will take you to the depth to realize you are (true self) consciousness, thus everything, you see, know, believe, and experience is nothing but consciousness. That is why Sri, Sage Sri Sankara Said:- Atman is Brahman – that is consciousness(soul) is —ultimate truth. Therefore, all the appearance and disappearance (three states) are nothing but consciousness. Thus, no second thing exists other than consciousness (soul). Only when you get a firm conviction about this truth you will be able to explain to others. It is very difficult to convince those who are stuck to their own accepted truth.