Before Rousseau, people made the mistake of treating children as merely adults shrunk small. The Bible and Freud go farther and tell us that an adult… - Paul Samuelson

Figure 12-6 pulls together in a simplified way the main elements of income determination. Without saving and investment, there would be a circular flow of income between business and the public: above, business pays out wages, interest, rents, and profits to the public in return for the services of labor and property; and below, the public pays consumption dollars to business in return for goods and services.
Realistically, we must recognize that the public will wish to save some of its income, as shown at the spigot Z. Hence, businesses cannot expect their consumption sales to be as large as the total of wages, interest, rents, and profits.

When I once called myself a “Sunday painter” dabbling in stochastic finance, that was not meant to belittle finance theory as a branch of serious economic theory. Such a peculiar view was expressed again and again by the late Milton Friedman, a dizzy view that I still find incomprehensible.

Modigliani's theory was a powerful searchlight on what was happening... It is the best explanation of what has actually been happening in the great swing of American life since the 1950's.