Money is not a part of the visible sector of the economy; people do not consume money. Money is not a physical factor of production, but rather a yardstick for measuring economic input, economic outtake and the relative values of the real goods and services of the economic world. Money provides a method of measuring obligations, rights, powers and privileges. It provides a means whereby certain individuals can accumulate claims against others, or against the economy as a whole, or against many economies.
Louis O. Kelso, Patricia Hetter Kelso (1967). “Two-factor Theory: the Economics of Reality; how to Turn Eighty Million Workers Into Capitalists on Borrowed Money, and Other Proposals”, New York : Vintage Books