In my experience, all great leaders share a singular and unmistakable "common denominator," reported Inc.'s Geoffrey James.

Is it maturity? No. Nobody would ever accuse Mark Zuckerberg of being "mature."

Youth? Again, no. Dole Foods CEO David H. Murdock is in his nineties.

Charisma? No way. Bill Gates has the charisma of a day-old mackerel.

Innovativeness? Nope. Coke's CEO Muhtar Kent arguably hasn't had a new idea in years.

Intelligence? Uh, no. Henry Ford had a notably low IQ.

Empathy? Certainly not. Steve Jobs was as unempathic as they come.

What, then, IS the common denominator?

Earlier this month I asked that question of Matt Tenney, author of the new (and excellent) book Serve to Be Great. His answer:

"Self-awareness."

And he's right.

As I think back on the hundreds of leaders I've interviewed over the decades, the ones who were truly great (by any reasonable standard) had a "presence" about them, a sense of power that transcended their position.

I now realize that the source of that power was that, unlike most people, these great leaders knew, in their heart of hearts, who they really were. Consider:

If you don't know exactly who you are, how can you possibly bring your strengths to bear, as leader or even as an individual contributor?

If you don't know exactly who you are, how can you possibly overcome the shortcomings and foibles that are obvious to everyone else?

If you don't know exactly who you are, everything you do is just an act. People will sense that you're disingenuous and look for leadership elsewhere.

So if you truly want to be a great leader, don't start by learning management technique. Instead, start self-assessment, the quest for the inner awareness that precedes and produces the highest levels of success.