Zuckerberg, who famously dropped out of Harvard to build Facebook, returned to deliver the commencement address. He told the JFK-janitor story — when Kennedy visited NASA and asked a janitor what he was doing, the man replied 'Mr. President, I'm helping put a man on the moon.' Zuckerberg argued that finding your own purpose wasn't enough; the challenge for their generation was creating a world where everyone has a sense of purpose, especially as technology and automation eliminate jobs and community membership declines.