While the existence of a soul is intuitively very unlikely considering modern psychology and neuroscience, there are several theoretical experiments that could be utilized to further disprove the existence of a soul:
- Using incredibly advanced biotechnology, amputate parts of a subject gradually and replace them with synthetic organs. Allow the patient to remain conscious and communicating (obviously under heavy anesthesia). As sections of the brain are removed, locations of personality, decision making, and consciousness will be pinpointed (along with various other regions; a rigorous protocol would glean much from this experiment).
- Clone a human being using conventional cloning techniques. Rear that human being in precisely the same environment as its twin. Similarity between the two will correlate very highly with similarity in environment and nurture, in every aspect (personality, decision making, behavior, etc.). Nature (genetic makeup) is kept constant while nurture is varied. If nature and nurture are identical and an identical person is produced, whence the soul?
- Perform a brain transplant, and question the subjects on self-identity. Admittedly, this could be interpreted merely as the brain being the vessel for the soul.
- Simply imagine that humans are material objects. In the future, it is conceivable that we will have the power to expertly craft identical material objects. We already understand the flow of chemical, electrical, and mechanical energy throughout the body, so we could effectively engineer an android that is indistinguishable from a natural human being. If this works, it will be evident that a soul is a superfluous notion. This is similar to item #1.