very simple, but very impressive proof for the existence of the soul.

 You say in daily life, "My body", "My Prana (energy)", "My mind", "My Indriya (senses)". This clearly denotes that the Self or Atman is entirely different from the body, the mind, the Prana and the Indriyas. The mind and the body are your servants or instruments. They are as much outside of you as these towels, chairs, cups are. You are holding the body just as you are holding a long walking stick in your hand. You are the possessor or proprietor of this body. The body is your property or possession. The body, the senses, the mind, the, etc., are not the soul, but belong to it.