Our biggest threat is not an asteroid about to crash into us, something we can do nothing about. Instead, all the major threats facing us today are problems entirely of our own making. And since we made the problems, we can also solve the problems.

In contrast [to trees and fish], oil, metals, and coal are not renewable; they don't reproduce, sprout, or have sex to produce baby oil droplets or coal nuggets.

Science is often misrepresented as "the body of knowledge acquired by performing replicated controlled experiments in the laboratory." Actually, science is something broader: the acquisition of reliable knowledge about the world.

Not until the beginning of the 20th century did Europe's urban populations finally become self-sustaining: before then, constant immigration of healthy peasants from the countryside was necessary to make up for the constant deaths of city dwellers from crowd diseases.

The rate of human invention is faster, and the rate of cultural loss is slower, in areas occupied by many competing societies with many individuals and in contact with societies elsewhere.

One person making a wrong decision affects the whole country.

No government is here forever. And there are other forces - the most potent force in our society, in fact, big business - doing good for the environment.