Everybody wants to live, and takes treatment when ill, spending any amount. Hence, the essential nature of man should be eternal existence. Even a fool thinks that he is wise. Everyone wants to show that he knows more than others. Nobody likes to be called a fool.
Children tease their parents with various sorts of questions.
The desire to know is ingrained in them. These indicate that our essential nature is knowledge. When a man laughs, people seldom ask why he is laughing. On the other hand when a man cries, everybody asks why he is crying. This shows that our essential nature is bliss.