Adam smith has authored a book “An inquiry into the nature and causes of the wealth of nations”.In this Adam Smith defined economics as a science of wealth. He proposed two requirements in his system: the market must be free from government intervention and competition must be in full range. But he put wealth above human. He described children and old age people as secondary, because they cannot contribute in production.
David Ricardo is most remembered for his “Theory of Comparative Advantage”. This theory deals with international trade where one country involves in export or import of goods and services with other countries.
Thomas Malthus had two major contributions to the modern economic system: the population theory and the theory of market gluts. Thomas Robert Malthus was the first economist to propose a systematic theory of population. He articulated his views regarding population in his famous book, Essay on the Principle of Population (1798). He stated that population, when unchecked, increases at a geometrical ratio while food production increases only in an arithmetical ratio.
John Meynard Keynes:
John Meynard Keynes revolutionized the economists’ conceptions about economics. He says that the state can stimulate economic growth and restore stability in the economy through expansionary policy like massive spending on infrastructure when demand is low and growth rate is falling. Theories of Keynes were presented in his book :General Theory of Employment, Interest and Money . He is also known as the father of world bank and IMF(International monetary fund)