ABSTRACT
The last 150 years or so has been a period of quite unprecedented social change. We have seen the application of science to the technology of production and destruction, as in the chemical industry, the electrical industry, automobiles and airplanes, and nuclear power and nuclear weapons. This period has also seen profound changes in social environments and institutions, such as the rise and now, as we have seen, the decay of centrally planned economies and welfare states. There has been a spectacular increase in the expectation of human life and a decline in infant mortality, resulting in an unprecedented population explosion. The human population of the earth has more than doubled in my own lifetime.
