If the mind-soul is to continue to live beyond this life, then the mind must be separate from the body. We know that all thought, all feeling, all emotion, consist of physiological functions of the brain. Everything from love, hate, hunger and sex are all combinations of chemical and electrical activity, complex as that may be. Just as our stomach digests food, breaking down complex proteins into simpler amino acids for growth and energy, so too our minds digest ideas, breaking them down with logic, and then determine which of several choices yields the highest probability of truth. It can be observed that the mind is born with the body, matures with the body, and ages.
Little children have small minds.
As their bodies grow, so too does their knowledge base. The mind becomes more powerful, as the body strengthens. When very old, as the body becomes feeble, so also does the mind. Just as the body suffers from disease, so too does the mind. A body raging with fever has a mind that suffers feverish delusions.