What makes a great leader? The answer, it would appear, depends on whom you ask. When the Wharton Business School recently drew up a list of the world's 25 most influential business leaders over the past 25 years, it came up with what can only be described as a rather eclectic mix.

Let me spare you the count: there were just two women (Mary Kay and Oprah Winfrey) and one dot-com CEO (Jeff Bezos) on the honour-roll, and the only person from a developing country to figure was Mohammed Yunus, the founder of Bangladesh's Grameen Bank.

To be sure, the list wasn't exactly global (with 23 Americans, the US bias was obvious), or even comprehensive (Sony's Akio Morita didn't make it).

Refreshingly, as the methodology indicated, the compilation had no pretensions of being either definitive or scientific. A jury of six -- which included Michael Useem, the director of Wharton's Center for Leadership and Change Management; Peter Cappelli, the director of the Center for Human Resources; and Raffi Amit, the director of the Goergen Entrepreneurial Research Program -- picked the top 25 from a short-list of 700 nominees.

To make the final cut, the jurors stipulated that a leader should have created new and profitable ideas; created new business opportunities or more fully exploited existing ones; caused or influenced dramatic change in a company or industry; inspired and transformed people; and affected political, civic or social change through achievement in the business or economic world.

The fact that Wharton's leadership experts found 25 people who met those criteria raised an intriguing possibility: had the list also revealed the rare qualities that only outstanding leaders seem to have?

Michael Useem, Wharton's best-known leadership guru, would only say: "The list we drew up shows that leadership comes in all shapes, sizes and styles." Clearly, there is no cookie-cutter for leadership; as the old saw goes, it's a problem that can only be solved one leader at a time.

Useem pointed out, some traits did distinguish outstanding leaders from the ordinary. In fact, there were three significant differences between those who made it into the top 25 and the remaining 675 who failed to make the cut. One, the best displayed the ability to not let up until the job was done.

Unlike most entrepreneurs who make their pile by cashing out, these leaders had vision -- and the passion and commitment required to realise the vision against all odds. Their willingness to stay in the game was reflected as much by the success of their enterprises as the endurance of their influence.

"Their resolve drives them to look for best practices, the best people," explains Useem. "Such leaders don't hesitate to fire even friends if they don't perform."

The importance that the Wharton panel attached to the social responsibility of business leaders was revealing. When most managers still don't get the fact that companies have greater responsibilities to society than ever, at least two leaders made the grade for doing the right thing by society, and not just their companies.

The manner in which former Johnson & Johnson CEO James Burke handled the crisis in 1982 when someone introduced cyanide in the company's painkillers, Tylenol, has become a textbook case for candor and honesty.

In the same vein, Mohammed Yunus was the first to recognise that lending to the poor could be a profitable business. Micro-lending programmes modelled after Grameen's have now spread to more than 100 countries.

Finally, Useem noticed that the top 25 showed a remarkable pattern in their ability to step out of comfort zones and into terror zones for the sake of their companies.

For instance, Andy Grove's only-the-paranoid-survive philosophy not only helped Intel reinvent itself, but it also taught the company to seek longevity by embracing risk. "Such leaders are always looking for the edge," adds Useem, pointing out that the Wharton list reaffirmed his commitment to unconventional methods for training leaders.

Useem's students routinely accompany him on treks to the far corners of the earth, like the Mount Everest base camp or the top of Ecuador's active volcano, Cotopaxi, to learn about teamwork, ethics and decision-making.

"Critical decisions on mountainous terrain can neither be postponed nor be flawed. Mountain climbers rarely get a second chance when things go wrong. Because climbing imposes a high premium on both speed and precision, mountains provide an exceptional lens through which to prepare for leadership decisions on terra firma," wrote Useem in Upward Bound, a book he co-edited last year.

Useem is the first to admit that not all great leaders know how to climb mountains; in fact, few do. However, most outstanding leaders do know how to keep moving mountains.

Manjari Raman is a Boston-based writer.

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