The poet has drawn our attention towards an eternal truth that what is impossible, can not be possible. But what is possible is always possible. We, the human beings can not challenge this law of nature. There are some examples to prove it, such as rising of the sun and moon, the formation of day and night, the cycle of birth and death, the high tide and the low tide. These incidents occur in a very natural way and we can not alter or make any change in them. To clarify it properly the poet gives another example that a cart can not move in the water and a boat can not swim on the land. Thus, what is impossible, can not be possible. But what is possible, is always possible. A fish can not live out of water. Similarly it is difficult to remove blackness from soot. Thus, a human being is totally helpless in front of the nature.