Today, let's consider your power to influence -- and to heal. 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.

A powerful thing happened the other day. I talked with a friend. He had a problem. He needed advice. I was feeling ineffective and depressed. I said, "Look, I'm too bummed out to be of any use to you."

I went away uneasy. We'd been so little use to each other. How much use is anyone to someone else who's down? That evening, the phone rang. He was back. "I have an idea for your program. Why don't you talk about the relative scale of cause and effect?"

I was puzzled. "What do you mean?" So he went on. "How many man-years have you spent writing your radio spot?" I calculated 2½ years. "Ok," he said, "How long have those programs run on the air?" This time I got only 32 hours.

He drove the point home. "That's 2½ years' work for only 32 hours of product! That looks pretty grim. -- Now, how many man-years have people spent listening to you?" This time I calculated 6000 years*. 6000 years would reach all the way back into the late Stone Age.

So ask that question in your life. Are you a schoolteacher? How vast is the spread of your effect in the world? Are you a shopkeeper? Leave off concerns about inventory and profit margin. Think about people you've supplied. Think about the reach of your influence into everyday life.

Are you a garbage collector or a physician? If you're either one, you need have little doubt about your value in thousands of lives. But some deal in more subtle services. How does a pure mathematician gauge his or her effect?

For most of us, life is a series of problems -- all imperfectly solved. The real fruit of our efforts lies somewhere on the other side of those problems. There, our creative best reaches people in far larger ways than it first might seem.

My friend made his point subtly and creatively. He gave me a way to see my work in more dramatic terms than I'd been able to.

But he also made the point in a second, less obvious, way. He hadn't just called to suggest a program idea at all. He'd called to cheer me up -- to express concern.

That's influence of a different order. And it's all too rare. He made his point and he role-modeled it. He did show me how our creative best has the power to influence. But he also showed me that it really does give us means to heal each other -- after all.

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

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*That was in l992.