Steve Jobs and Jeff Bezos' mentor used a simple test to figure out who is a true leader

You can have the most impressive title in the world and still not be a leader.

According to the late Bill Campbell, who established a reputation as the "coach" of Silicon Valley, only one thing determines whether or not you're a leader: the opinions of those you're supposed to be leading.

A former Columbia University football player and coach, Campbell went on to work with and mentor with some of the biggest names in tech, including Steve Jobs, Jeff Bezos, Larry Page, and Eric Schmidt.

Former Apple CEO John Sculley poached Campbell, hiring him away from Kodak to work as Apple's VP of marketing.

Sculley shared one of the best pieces of advice Campbell ever gave him: "Your title makes you a manager. Your people will decide if you're a leader, and it's up to you to live up to that."

Campbell himself told Sculley he'd come to that realization about leadership from working with Jobs.

"The reality is that you have to earn leadership from the people that you're working with and who are working for you," Sculley told Business Insider. "The title doesn't mean much unless you can earn their respect as a leader."

Later in his career, Campbell served on Apple's board of directors. He went on to also become CEO of Intuit from 1994 to 1998 and eventually became the chairman of the tech company's board.

Current Intuit CEO Brad Smith said he got the same advice on leadership from Campbell, too. Sculley and Smith both said it was the best career advice they'd ever received, and that it's stuck with them ever since.

"Basically, how you make that happen is if you believe that leadership is not about putting greatness into people, leadership is about recognizing that there's a greatness in everyone and your job is to create an environment where that greatness can emerge," Smith told Business Insider. "That's our definition of leadership. We don't think leadership is the same as people management."