The Principles of Economics
Marshall's influence on modifying economic thought is difficult to deny. He popularized the use of supply and demand functions as tools of price determination (previously discovered independently by Cournot); modern economists owe the linkage between price shifts and curve shifts to Marshall. Marshall was an important part of the "marginalist revolution;" the idea that consumers attempt to adjust consumption until marginal utility equals the price was another of his contributions. The price elasticity of demand was presented by Marshall as an extension of these ideas. Economic welfare, divided into producer surplus and consumer surplus, was contributed by Marshall, and indeed, the two are sometimes described eponymously as 'Marshallian surplus.' He used this idea of surplus to rigorously analyze the effect of taxes and price shifts on market welfare. Marshall also identified quasi-rents.
Principles of Economicsis a leading political economy or economics textbook of Alfred Marshall (1842–1924), first published in 1890. It ran into many editions and was the standard text for generations of economics students.
Political Economy or 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.