Biden was in Philadelphia on Monday night to see his 28-year-old daughter, Ashley, receive a master's degree in social work.
A pool report released by the White House says Biden told about 150 graduates of the university's School of Social Policy and Practice they could bring positive change to the world by empowering others.
Biden told the graduates their belief they could make things better was the "fuel" of social change. But he said if they ever lose that optimism they should leave the profession.
The vice president also warned against abuse of power at every level.
