When one says, I see, this means that he sees with his eyes or with his spectacles; he sees with the instrument of sight. If the instrument of sight is broken or becomes diseased or incapable of acting, then he, as the seer, also ceases to act. Similarly, in this material body, at the present moment the living soul is acting, and when the material body, due to its incapability to function, ceases, he also ceases to perform his reactionary activities. When ones instrument of action is broken and cannot function, that is called death. Again, when one gets a new instrument for action, that is called birth. This process of birth and death is going on at every moment, by constant bodily change. The final change is called death, and acceptance of a new body is called birth. That is the solution to the question of birth and death. Actually, the living entity has neither birth nor death, but is eternal. As confirmed in Bhagavad-gita, na hanyate hanyamane sarire: [Bg. 2.20] the living entity never dies, even after the death or annihilation of this material body.