Alfred Marshall (1842-1924)
"Economics is a study of mankind in the ordinary business of life; it examines that part of individual and social action which is most closely connected with the attainment and with the use of the material requisites of wellbeing"

Lionel Robbins (1898-1984)
Lionel Robbins in a 1932 essay: Economics is "the science which studies human behavior as a relationship between ends and scarce means which have alternative uses." Scarcity means that available resources are insufficient to satisfy all wants and needs. Absent scarcity and alternative uses of available resources, there is no economic problem.

John Maynard Keynes (1883-1946)
“The long run is a misleading guide to current affairs. In the long run we are all dead.”

Ludwig von Mises (1881-1973)
"Economics deals with society's fundamental problems; it concerns everyone and belongs to all. It is the main and proper study of every citizen."

Joseph Schumpeter (1883-1950)
“The process of Creative Destruction is the essential fact about capitalism. It is what capitalism consists in and what every capitalist concern has got to live in. . . .”

Karl Marx (1818-1883)
“The development of Modern Industry, therefore, cuts from under its feet the very foundation on which the bourgeoisie produces and appropriates products. What the bourgeoisie therefore produces, above all, are its own grave-diggers. Its fall and the victory of the proletariat are equally inevitable."

Milton Friedman (1912-2006)
“The great virtue of a free market system is that it does not care what color people are; it does not care what their religion is; it only cares whether they can produce something you want to buy. It is the most effective system we have discovered to enable people who hate one another to deal with one another and help one another.”

David Ricardo (1772-1823)
"Profits depend on high or low wages, wages on the price of necessaries, and the price of necessaries chiefly on the price of food."

Adam Smith (1723-1790)
"It is not from the benevolence of the butcher, the brewer, or the baker that we expect our dinner, but from their regard to their own interest. We address ourselves, not to their humanity but to their self-love, and never talk to them of our own necessities but of their advantages."

Thomas Robert Malthus (1766-1834)
“Population, when unchecked, increases in a geometrical ratio”

Bernard M. Baruch (1870-1965)
“Millions saw the apple fall, but Newton was the one who asked why.”

Mary Paley Marshall (1850-1944)
It was published in our joint names in 1879. Alfred insisted on this, though as time went on I realized that it had to be really his book, the latter half being almost entirely his and containing the germs of much that appeared later in the Principles of Economics. He never liked the little book for it offended against his belief that "every dogma that is short and simple is false" and he said about it "you can't afford to tell the truth for half-a-crown".

Friedrich August von Hayek (1899-1992)
If we wish to preserve a free society, it is essential that we recognize that the desirability of a particular object is not sufficient justification for the use of coercion.