DNA has been aptly described as the first three-dimensional Xerox machine.

With laissez-faire and price atomic, ecology's uneconomic, But with another kind of logic economy's unecologic.

It is clear that the building of models is not a purely mechanical process but requires skill of a high order - not merely mathematical skill but a sensitivity to the relative importance of different factors and a critical, almost an artistic, faculty in the selection of behaviour equations which are reasonable, tentative hypotheses in explaining the behaviour of actual economies.

Because of his capacity for abstract communications and language and his ability to enter in imagination into the lives of others, man is able to build organizations of a size and complexity far beyond those of the lower animals.

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.

We should always bear in mind that numbers represent a simplification of reality.

[In science any model depends on a pre-chosen taxonomy] a set of classifications into which we divide the enormous complexity of the real world... Land, labor, and capital are extremely heterogeneous aggregates, not much better than earth, air, fire, and water.