sources in certain ways, a process of social learning may, over time, narrow differences among them in the values they assign to the consequences. The decline in the number of Americans who smoke cigarettes—the increasing number who agree smoking is not a good idea—seems clearly to reflect a process of social learning of this sort.

This line of argument suggests that if we are to succeed in shaping policies to ensure sustainable management of natural and ecological resources, we badly need more information about the possibilities for substitution of human-made resources for those represented by the natural system and about the processes by which human values are shaped over time. There is a challenge here for joint work among economists and other social scientists, ecologists, and philosophers. It is a daunting challenge. Responding to it also has promise of high payoff in betterment of the human condition.


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Circacy-Wantrup, S. V. 1952. Resource Conservation. Berkeley, Calif.: University of California Press.

Daly, H., and J. Cobb. 1989. For the Common Good. Boston, Mass.: Beacon Press.

Ehrlich, P. R., and A. H. Ehrlich. 1990. The Population Explosion. New York: Simon and Schuster.

Norton, B. 1992. Sustainability, human welfare and ecosystem health. Environmental Values 1(2)(summer):97-111.

Simon, L. 1981. The Ultimate Resource. Princeton, N.J.: Princeton University Press.

World Commission on Environment and Development. 1987. Our Common Future. New York: Oxford University Press.

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