You can find the answer to this question at the end of this chapter. The answer is that John the Savage tells Mustapha Mond that he claims the right to be unhappy.
John has been talking to Mond about philosophical issues. He wants to know if it is not important to have danger and anger and sadness at times in human beings' lives. Mond tells him those things are important but that you can get their benefits with the VPS and not have to have the down sides.
John responds by saying that he claims the right to be unhappy.