Today, invention goes looking for her mother. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

"Who's the mother of invention?" People often ask me that. "Who's the mother of invention?" There are so many candidates. Yet the list always begins with necessity and gain.

Of course, invention serves necessity. But do you really believe necessity can drive the inventive muse? I have the same problem with profit. Invention can gain an inventor money. But when has a craving for gain ever opened anyone's mind? You can't really take necessity or money seriously as parents of invention.

Let's muddy the water and ask, "Who's the father of invention?" At the risk of gender stereotyping, I'll ask, "If mother nurtures and sustains invention, who's the seminal initiator?"

We've looked at hundreds of case histories in this series. They tell us a lot about nurture. I'll claim flatly that freedom is the nurturing mother of invention.

Invention always flourishes when people are free -- when they enjoy intellectual permissiveness. Every time personal liberty opens up in a society, invention flourishes. Look at Hellenistic North Africa, late 18th-century England, or 19th-century America.

Invention not only thrives in freedom. It's also a door out of oppression. The theme of invention runs through the literature of slavery, prisons, and concentration camps. An unfree person goes to great lengths to claim a quiet place in his own head -- a place to be free. Invention is a way to do that. John Bunyan wrote Pilgrim's Progress in prison. Evariste Galois created modern algebraic theory in prison when he was only 20.

But the primal, driving, seminal, origin of invention has to be pleasure. Who doesn't crave, just once in a lifetime crowded with pain, problems, and incompleteness, to shout, Eureka? Who doesn't understand in his bones how Archimedes leapt from the bath and ran naked down the street, shouting, "I've found it! I've found it! I've found it!"

If you've once tasted the pleasure of creating something good and new, you'll want to return to the moment at all costs. The only way to walk away from such pleasure, once you've known it, is to let something die inside you. Some inventors have done that -- invented one thing, then lived off the profits. But not the good ones. People like Edison, Bell, and Einstein kept coming back to that well of life until the day they died.

Make no mistake about it. The parents of invention are pleasure and freedom. And I tell you, they are the finest parents any child could ever claim.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

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