The spirit, Prana existing in every living being was no different than souls’ atmans. Call it a soul or spirit means the same. The consciousness, spirit existing in all living beings is beyond human comprehension. It was more subtle than anything perceived by human intellect till date, even minute than God particle researched by scientists.
No matter how much science progresses, none world over would be able to reach, comprehend the entity we called soul, spirit.
Before the present cosmos came into being existed cluster of pure souls atmans, nothing more. No sooner big bang explosion occurred all pure souls atmans, spirits scattered all over cosmos at unimaginable speeds. In the melee the hurtling souls atmans gathered impurities and to cleanse self of dross impurities within starts cosmic life cycle of every soul atman, the spirit.
As per doctrine of Maya propagated by Adi Shankaracharya other than world of spirits, souls atmans nothing existed in cosmos. Broken down to basic building block of cosmos, everything visible in this world was just a cluster of atoms and molecules including all human forms. When viewed from senses point of view things appeared solid, in reality all was gaseous formation.
Soul, the spirit is the Prana existing in all living beings that was the only and real truth of life.