Adding more people causes problems. But people are also the means to solve these problems. The main fuel to speed the world’s progress is our stock of knowledge; the brakes are our lack of imagination and unsound social regulations of these activities. The ultimate resource is people—especially skilled, spirited, and hopeful young people endowed with liberty—who will exert their wills and imaginations for their own benefits, and so inevitably they will benefit the rest of us as well.

Energy is the master resource, because energy enables us to convert one material into another. As natural scientists continue to learn more about the transformation of materials from one form to another with the aid of energy, energy will be even more important.

The world's problem is not too many people, but lack of political and economic freedom.

Human beings create more than they destroy.

This is my long-run forecast in brief: The material conditions of life will continue to get better for most people, in most countries, most of the time, indefinitely. Within a century or two, all nations and most of humanity will be at or above today's Western living standards. I also speculate, however, that many people will continue to think and say that the conditions of life are getting worse.

People call me an optimist, but I'm really an appreciator ... years ago, I was cured of a badly infected finger with antibiotics when once my doctor could have recommended only a hot water soak or, eventually, surgery.... When I was six years old and had scarlet fever, the first of the miracle drugs, sulfanilamide, saved my life. I'm grateful for computers and photocopiers ... I appreciate where we've come from.

The main fuel to speed the world's progress is our stock of knowledge, and the brake is our lack of imagination.