Bill and Melinda Gates

Gates, when you sit down with him in his Redmond office, rocks back and forth as he falls into a reverie about "the world-health thing." He says, "The more people know about this--about the millions of lives that can be saved, about the millions of children who are dying of disease every year that we have cures for--then how can you not do something about it? The most important priority for me is saying we could save millions of lives a year." That is a heady thought even for the richest man in the world. How many of us will ever be able to say we saved millions of lives?

For Gates, that prospect blunts the criticism of those who say his generosity is meant to burnish his image amid the Justice Department's antitrust suit against his company. (Though the Bill and Melinda Gates Foundation was founded in 1997, a year before the suit was filed, he has accelerated his donating schedule in the 16 months of the trial.) "I have a high enough level of visibility that people will second-guess anything I do," Gates says, shrugging. He has come to see his life as something of a tripod: there are his wife and children, his company and "this other area, in philanthropy, where I'm seeing that by engaging the smart people and highlighting the possibilities, there's a chance to do something that every day I feel good about."