I challenge you to join the struggle of the United Farm Workers. And if you don't join our cause, then seek out the many organizations seeking peaceful social change. Seek out the many outstanding leaders who will speak to you this week, and make a difference. —"Lessons of Dr. Martin Luther King, Jr.," Cesar Chavez This passage shows that Chavez’s main purpose is to urge people to seek social change through nonviolent action. to show the struggle of the United Farm Workers. to get the reader to join many organizations. to listen to the many outstanding leaders.