This is our disease. Therefore this disease . . . This disease means birth, death, old age and disease. So as soon as you accept this body, material body, you become subjected to the four laws of material nature. These four laws of material nature are that as soon as you've accepted this body, then you must accept death. Anything which is born must meet death also. Birth, death. And in the via media there is old age and disease. This body, I have got, you have got, everyone. There is a death of getting this body, and there will be a death of leaving this body. And between these two deaths there are so many other miserable conditions. They are summarized: old age and disease.
But the real science is that "I am the soul. I am the part and parcel of the Supreme Lord. So Supreme Lord, God, is eternal. I am also eternal." These things are described. Na hanyate hanyamāne śarīre (BG 2.20). As God . . . We are as good as God, at least in quality, not in quantity. We are . . . Just like a drop of seawater is as good as the seawater in quality—the whole seawater is also salty, and the drop of seawater is also salty—similarly, we have got all the chemical composition, or qualities, of God. Now, God is eternal; therefore we must be eternal. That is stated in the Bhagavad-gītā. Na hanyate hanyamāne śarīre (BG 2.20). After destruction of this body, the soul is never destroyed. This is our real, constitutional position. Then why we have accepted this changing process: birth, death, old age and disease? This is our material life.