Economists (and others) who are satisfied with nature-free equations develop a dangerous hubris about the potency of our species

The rational man finds that his share of the cost of the wastes he discharges into the commons is less than the cost of purifying his wastes before releasing them.

Ecology is the overall science of which economics is a minor speciality.

The only kind of coercion I recommend is mutual coercion, mutually agreed upon by the majority of the people affected.

In a competitive world of limited resources, total freedom of individual action is intolerable

Society does not need more children; but it does need more loved children. Quite literally, we cannot afford unloved children - but we pay heavily for them every day. There should not be the slightest communal concern when a woman elects to destroy the life of her thousandth-of-an-ounce embryo. But all society should rise up in alarm when it hears that a baby that is not wanted is about to be born.

No one should be able to enter a wilderness by mechanical means.