The ideas of economists and political philosophers, both when they are right and when they are wrong are more powerful than is commonly understood. I… - John Maynard Keynes

The general theory of economic equilibrium was strengthened and made effective as an organon of thought by two powerful subsidiary conceptions — the Margin and Substitution. The notion of the Margin was extended beyond utility to describe the equilibrium point in given conditions of any economic factor which can be regarded as capable of small variations about a given value,or in its functional relation to a given value.

My feelings about Das Kapital are the same as my feelings about the Koran. I know that it is historically important and I know that many people, not all of whom are idiots, find it a sort of Rock of Ages and containing inspiration. Yet when I look into it, it is to me inexplicable that it can have this effect. Its dreary, out-of-date, academic controversialising seems so extraordinarily unsuitable as material for the purpose … How could either of these books carry fire and sword round half the world? It beats me. [writing to George Bernard Shaw]

It is because particular individuals, fortunate in situation or in abilities, are able to take advantage of uncertainty and ignorance, and also because for the same reason big business is often a lottery, that great inequalities of wealth come about; and these same factors are also the cause of the Unemployment of Labour, or the disappointment of reasonable business expectations, and of the impairment of efficiency and production.