The evolutionary vision is agnostic in regard to systems in the universe of greater complexity than those of which human beings have clear knowledge.

The ability to work with systems of general equilibrium is perhaps one of the most important skills of the economist - a skill which he shares with many other scientists, but in which he has perhaps a certain comparative advantage.

The concept of need is often looked upon rather unfavorably by economists, in contrast with the concept of demand. Both, however, have their own strengths and weaknesses. The need concept is criticized as being too mechanical, as denying the autonomy and individuality of the human person, and as implying that the human being is a machine which "needs" fuel in the shape of food, engine dope in the shape of medicine, and spare parts provided by the surgeon.

Reality, in its quantitative aspect, must be considered as a system of populations... The general study of the equilibria and dynamics of populations seems to have no name; but as it has probably reached its highest development in the biological study known as 'ecology,' this name may well be given to it.

One reason why the progressive state is 'cheerful' is that social conflict is diminished by it.

The discounting presumably is to be done for each period of time at that rate of interest which represents the alternative cost of employing capital in the occupation in question; that is, at the rate which the entrepreneur could obtain in other investments

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.