[There will be movement toward] behavioral economics... [which] involves study of those aspects of men's images, or cognitive and affective structures that are more relevant to economic decisions.

In calling society an ecological system we are not merely using an analogy; society is an example of the general concept of an "ecosystem" that is, an ecological system of which biological systems - forests, fields, swamps - are other examples.

It is almost as hard to define mathematics as it is to define economics, and one is tempted to fall back on the famous old definition attributed to Jacob Viner, "Economics is what economists do," and say that mathematics is what mathematicians do. A large part of mathematics deals with the formal relations of quantities or numbers.

Political conflict rests to a very large extent on a universal ignorance of consequences, as the people who are benefited by any particular act or policy are rarely those who struggled for it, and the people who are injured are rarely those who opposed it.

Conventions of generality and mathematical elegance may be just as much barriers to the attainment and diffusion of knowledge as may contentment with particularity and literary vagueness... It may well be that the slovenly and literary borderland between economics and sociology will be the most fruitful building ground during the years to come and that mathematical economics will remain too flawless in its perfection to be very fruitful.

One of the most important skills of the economist, therefore, is that of simplification of the model. Two important methods of simplification have been developed by economists. One is the method of partial equilibrium analysis (or microeconomics), generally associated with the name of Alfred Marshall and the other is the method of aggregation (or macro-economics), associated with the name of John Maynard Keynes.

The social dynamics of human history, even more than that of biological evolution, illustrate the fundamental principle of ecological evolution - that everything depends on everything else. The nine elements that we have described in societal evolution of the three families of phenotypes - the phyla of things, organizations and people, the genetic bases in knowledge operating through energy and materials to produce phenotypes, and the three bonding relations of threat, integration and exchange - all interact on each other.