Facebook (FB) CEO Mark Zuckerberg, 33, took the stage at Harvard University’s 366th commencement ceremony on Thursday, and implored the graduating class of 2017 to create a world where everyone has a sense of purpose.

“Purpose is that feeling, that you are a part of something bigger than yourself,” Zuckerberg said. “That you are needed and that you have something better to work for … Purpose is what creates true happiness.”

Zuckerberg added: “The challenge of our generation is to create a world where everyone has a sense of purpose.”

Zuckerberg’s speech, which at times sounded more like a stump speech than a commencement address, touched on a variety of topics ranging from social issues, to criminal justice reform and immigration. But the CEO primarily focused on the need for graduates to bring a sense of purpose to their lives and the lives of others.

“It’s not enough to have that purpose yourself,” he said. “You also have to create a sense of purpose for others.”

Zuckerberg told the rain-soaked audience that millennials have reached a point where they have to undertake great efforts just as previous generations sent humans to space and constructed massive public works projects.

The Facebook founder said graduates should work to help combat climate change, find cures for diseases, ensure everyone is given a chance at an education and even potentially receive a universal basic income.

From Harvard dropout to billionaire

Zuckerberg enrolled at Harvard as part of the class of 2006. In 2004, he and four friends began working on a campus-only social network that would become thefacebook.com. They eventually expanded the platform to other individuals with college email accounts and, finally, the world.

But as he was turning Facebook into the behemoth that would eventually make him one of the richest people on Earth, Zuckerberg decided he didn’t have time to complete his degree. He left Harvard his sophomore year.

Since Zuckerberg left Harvard, Facebook has become one of the most popular websites in the world behind just Google and YouTube, according to web traffic tracker Alexa. The site has made Zuckerberg a billionaire several times over. He now receives an annual salary of just $1 and has dedicated a large chunk of his time to philanthropic efforts.

Facebook, however, hasn’t been without its controversies. Outside of the lawsuits filed against Zuckerberg related to who helped him build the network, the site and app have been roundly criticized for serving as gateways for the spread of “fake news” in the run-up to the 2016 election.