Religious reasons, which is no reason. I notice Skeptic had a review of Dennett's book, Darwin's Dangerous Idea. Religious reasons amount to what Dennett terms "skyhooks." Do you believe in skyhooks? I don't.

In a finite world this means that the per capita share of the world's goods must steadily decrease.

It is a mistake to think that we can control the breeding of mankind in the long run by an appeal to conscience.

An attack on values is inevitably seen as an act of subversion.

However, I think the major opposition to ecology has deeper roots than mere economics; ecology threatens widely held values so fundamental that they must be called religious.

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.

Using the commons as a cesspool does not harm the general public under frontier conditions, because there is no public, the same behavior in a metropolis is unbearable.