In an approximate way, the logic of commons has been understood for a long time, perhaps since the discovery of agriculture or the invention of private property in real estate.

In the specific case of abortion, the matter is particularly easy in that no woman wants a late abortion. Once abortion was made legal, the age of the aborted fetus went down. The slope slipped in the other direction. If we legalize RU-486 and other similar new drugs, the age will fall to one week or less and start approaching zero. The slippery slope will slide in the other direction. The only reason we have late abortions is because we make early abortion difficult.

You cannot do only one thing.

The optimum population is, then, less than the maximum.

The morality of an act is a function of the state of the system at the time it is performed.

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

Never globalize a problem if it can possibly be dealt with locally.