The population problem has no technical solution; it requires a fundamental extension in morality.

The three filters [against folly] operate through these particular questions: Literacy: What are the words? Numeracy: What are the numbers? Ecolacy: And then what?

Numeracy: 1. The art of putting numbers to things, that is, assigning amounts to variables in order that practical decisions may be reach. 2. That aspect of education (beyond mere literacy) which takes account of quantitative aspects of reality.

We can't cure a shortage by increasing the supply.

The exquisite sight, sound, and smell of wilderness is many times more powerful if it is earned through physical achievement, if it comes at the end of a long and fatiguing trip for which vigorous good health is necessary. Practically speaking, this means that no one should be able to enter a wilderness by mechanical means.

Indeed, our particular concept of private property, which deters us from exhausting the positive resources of the earth, favors pollution.

Ecological differentiation is the necessary condition for coexistence.