Here two words नदी and समुद्र are very specific. A river originates from some place flows towards the sea and in the end merges into the sea. This 'Nyaya' has been conceptualized on the basis of this kind of river sea relationship.
River possesses its own independent existence from its source till it merges into the sea. The when it merges into the sea, it loses it independent existence. Now river becomes the sea as it takes the from of sea. Here the ending of the independent existence of the river is not its destruction but it is its transformation and that too a qualitative or progressive one. From this, man has to learn that just like a river a person's independent life should be such that it should be such that it should towards society or nation. By leading an independent life one has to reach the society and the nation and after reaching there he has to end his own independent existence. In this way, a person ceases to be a person and becomes a society or a nation itself.
For example, there is a child. He takes birth in some family and here he lives an independent life. He has a specific name. As the time passed the child grew and became an independent person. The present 'Nyaya" teaches that this person must heard towards the nation.His goal must be to become a member of his nation. With the passage of time. When a person becomes a member, a part of a nation he has to forget his own identity and has to think of himself as a part of a nation. If every person lives life like this the nation always remain prosperous as the sea remains so with the merging of a river into the sea.