To this year’s graduates of the “world’s leading university for experiential learning,” Aimée Mullins made the case for the benefits of inexperience—for the “serendipity of surprise” that can only sprout when we leave preconceived notions at the door.

“I want to focus today on the power of the unknown, of embracing not knowing,” Mullins said in her Commencement address to roughly 4,000 Northeastern graduates at TD Garden on Friday. “When we trust what we know to be absolute, we limit our ability to have new perceptions and insights that would allow us to innovate.

“I’d like you to remember that naiveté, curiosity, and daydreaming are tools for building a better life, and you should be reaching into your toolbox for them often,” Mullins said.

The graduates, though, need not worry about being unprepared to use these tools.

“Your co-ops and other unfamiliar experiences have required you to act amidst uncertainty, to be open to surprise, to push outside your comfort zone, and to dream up solutions to problems you were encountering for the first time,” Mullins said.

Think about it. Every time you solved a new puzzle — on a co-op job or in the research lab — you weren’t allowing yourself to be disabled by your mind telling you that something was impossible just because you’d never done it before,” she said. “You used your naiveté to face and fix a problem without knowing or worrying about the ‘shoulds.’ All invention and innovation is born of this mindset.

Aimée Mullins, 2018 Commencement speaker

Her speech was punctuated with wry remarks that brought laughs from the packed TD Garden. Noting that graduation is a rite of passage into adulthood, for example, she quipped, “You can’t ask your parents for money anymore.”

Her advice to the graduates was born of her own experience, or perhaps, from having experienced that same “not knowing.”

Mullins is an actor in the Emmy-nominated TV show Stranger Things; a world record-setting sprinter; a double below-the-knee amputee who pioneered the woven carbon-fiber prostheses that are now the international standard for amputee runners; a muse and runway model of iconic fashion designer Alexander McQueen; a National Women’s Hall of Fame inductee; and an advocate for reforming the societal mindset around “disability” whose TED Talks have been viewed more than 7 million times.

But her life began with uncertainty.

Mullins was born without fibulae, and on her first birthday, her legs were amputated below the knees. At the time, doctors told her parents she’d never walk, never lead a “normal” life.

Some might have pulled up short at this seemingly immovable brick wall of an obstacle. Mullins scaled instead.

She described a collegiate track meet where she competed in the long jump as the only female athlete. At the time, she was running on heavy wooden legs. Another double below-the-knee amputee at the race approached during the event and explained that “we’re not supposed to be able to do the long jump, because we don’t have a good foot to push off with,” Mullins recalled. “Well,” she remembered saying, “Nobody told me that, and I’ve already jumped twice, so I might as well keep doing it.”

That day, she came within four inches of the U.S. long jump record. A year later, she set the world record in the long jump, still having been the only double below-the-knee amputee to do it.

Mullins also described her drive to become “the fastest woman on the planet with prosthetic legs,” meaning she would have to abandon her “trusty” wooden legs. Rather than starting from the conventional baseline of human legs, though, she took a different tack.

“If I were trying to become the fastest woman on the planet with artificial legs, and I didn’t have to have human legs, then why were we looking at them? Why weren’t we looking at the fastest thing that runs? Which is a cheetah,” she said.

I’d like you to remember that naiveté, curiosity, and daydreaming are tools for building a better life, and you should be reaching into your toolbox for them often.

Aimée Mullins, 2018 Commencement speaker

Thus was born first-of-their-kind carbon-fiber prostheses designed to imitate the hind legs of a cheetah — protheses that have since become the international standard for amputee sprinters.

In short: “Not knowing that you can’t do something can be an incredible asset in life,” Mullins said.

“Think about it. Every time you solved a new puzzle — on a co-op job or in the research lab — you weren’t allowing yourself to be disabled by your mind telling you that something was impossible just because you’d never done it before,” she said. “You used your naiveté to face and fix a problem without knowing or worrying about the ‘shoulds.’ All invention and innovation is born of this mindset.”

The flip side of naiveite is curiosity, Mullins said.

“You do better just starting something than you do thinking about starting something,” Mullins said. “Starting is using your curiosity as an active tool to learn and discover. It’s about getting comfortable with being uncomfortable.”

Of course, being curious also means exploring the things that run counter to engrained interests. Take, for example, the now-defunct Chet’s Video and Candy Shoppe in Marblehead, Massachusetts.

Mullins described the store’s shelves, which “invited you to explore hundreds of diverse movie titles — indiscriminate of your presumed likes and dislikes.

“Reside in the mindset of Chet’s video store and you won’t get trapped by what some other person, company, or institution thinks your choices should be,” she said.

Another of Mullins’ tools for building a better life is daydreaming. She urged graduates to go beyond what they’ve learned so far and spend time imagining what could be.

For all their myriad benefits, Mullins pointed out that artificially intelligent programs cannot yet make choices that involve unknowns; they must rely on the information they’re fed.

“They are limited by what they’ve learned,” she said. “People, on the other hand, are freed by what they can imagine.”

Indeed, Mullins said she’s spent considerable time imagining, daydreaming.

“I spent a lot of time in hospitals as a child, and when I couldn’t actually leave the hospital bed with two full plaster casts on my legs, I daydreamed my way out,” she said. She then went on to daydream a wildly successful future into existence.

Mullins has been honored by prestigious institutions such as the Smithsonian, the Metropolitan Museum of Art, the NCAA Hall of Fame, the Victoria and Albert Museum, the Tate Modern, and the Track and Field Hall of Fame. The Women’s Museum recognized her among the “Greatest American Women of the 20th Century,” and in 2017 she became one of the youngest inductees to the National Women’s Hall of Fame.

“I designed my future by daydreaming it, because daydreaming is the bridge between imagining and creating something,” Mullins told the graduates. “Daydreaming helps us see a path through the limitless possibilities of the imagination so that the unknown, unexperienced, or the unreal takes shape in our mind’s eye and become seen, known, and ultimately much closer to becoming real.”

She urged the soon-to-be-graduates in the room, on the threshold of great possibility, to reach into their toolboxes for those well-worn instruments of naiveté, curiosity, and imagination forged through their experience at Northeastern and wield them with confidence.

“Northeastern University Class of 2018, keep that going,” she said. “This commencement doesn’t reference a finish line; it speaks to beginnings. Commence each day with a little bit of that just-born feeling. Bring your toolbox from childhood and use the tools.”