His master stays still.
The next day, he asks the same question, and the master still stays on the same stillness.
One day he got bored and says, "master why don't you tell me what is silent?".
The master smiles and says, "I did show you all the time, didn't you see it?".
Then the pupil realize his mistake. He only pursued answer but not reality about silent. Something that can not be share, isn't silent - but something that can be share - still isn't silent. By negating all this, there is a silent.