“Assumptions are the death of possibilities. ”  —James Mapes

• Women don’t have the stamina to ascend Everest.
• Humans can’t fly to the moon.
• The human body can’t run a mile in under four minutes.
• Women are too emotional to be leaders.
• The sun revolves around the earth (which, by the way, is flat.)
• Telephones are only for talking and listening.
• Animal species never change.
• And I (Margie) can never run 10 miles… in a row. Never ever.

Some of these assumptions had the force of science behind them—others just the force of habit. All of them seem foolish in retrospect.

And the only reason any of them collapsed was because someone had the courage to challenge the status quo, to push back against “the truth,” to part with tradition and to ask questions about why things are the way they are and how they might be instead.

Courageous thinking, from Henry David Thoreau’s blunt naturalism to Martin Luther King’s calls for justice, involves risk. It can make people very uncomfortable, invite criticism (if not outright ostracism) and be quietly disturbing to those whose view of the world is built on assumptions. But courageous thinking is also what promotes progress in our lives, organizations, government and society.

Earlier this year I accomplished what I had previously thought an impossibility: I ran 10 miles… in a row… without stopping. Until I began to train, I’d never run more than three miles (and that was only once). I just didn’t think my body was made for running. But I was willing to prove myself wrong and did. If you’d seen my face as I crossed the finish line you’d have thought I’d just won an Olympic marathon—such was my sense of accomplishment and delight. Next goal: half marathon!

Sometimes when we think outside the box, we get it wrong. Sometimes when we take risks, we fail. And sometimes, despite our very best efforts to achieve a particular outcome, we fall short. But that doesn’t mean we should quit trying. What matters most is not whether our assumptions, or efforts to disprove them, propel us to grand new heights (I’m thinking lunar landing here). Rather, what matters most is that we have the courage to challenge our own beliefs, however attached we are to them—to think bigger about what is possible, to ask more questions than we have answers and to inspire others to do the same.

Too many women make unwarranted assumptions about their capabilities.

• I can’t be a good mother and have a rewarding career.
• I don’t have what it takes.
• Management never takes me seriously.
• I’m not smart enough to make it to the top.
• I can’t handle confrontation—never have, never will.
• I’ll never earn the income or get the recognition I deserve.
• The old boys club is still propping the glass ceiling firmly above my head.

In the last month I’ve experienced a hurricane, an earthquake and flash flooding. I’ve arranged 15 interviews with CEO’s for my next book on corporate courage. I’ve dined with a British aristocrat, made two trips to the emergency room with my kids (they’re fine), and finally, just days ago, I was informed that E = mc2 may no longer be a universal truth.

Life is way too unpredictable and mysterious to ever be completely understood, so you probably shouldn’t assume that you know your limits. There’s no guarantee that your assumptions will hold true for another day, much less for the rest of your life.

The fact is, you have no idea what you could do if you put your mind to it. (Good thing the Wright brothers weren’t willing to settle for consensus opinion on the possibility of human flight.) Just know that you can limit yourself profoundly when you start treating your assumptions as the truth. They may not hold.

Be bold! Your life will shrink or expand in proportion to your willingness to “prove yourself wrong.”