Marginalist, Neoclassical and Welfare Economists

His book Principles of Economics (1890) was the dominant economic textbook in England for many years, and brought the ideas of supply and demand, marginal utility, and costs of production into a coherent whole, popularizing the modern neoclassical approach which dominates microeconomics to this day.

Trained in physics and mathematics, he became a polymath whose genius radiated into nearly all other major fields of knowledge." He introduced the concept of Pareto efficiency and helped develop the field of microeconomics.

He formulated the marginal theory of value (independently of William Stanley Jevons and Carl Menger) and pioneered the development of general equilibrium theory.

In so doing, it expounded upon the "final" (marginal) utility theory of value.

His work covered various fields of economics, particularly welfare economics, but also included business cycle theory, unemployment, public finance, index numbers, and measurement of national output.

His contributions to social choice theory, notably his "impossibility theorem", and his work on general equilibrium analysis are significant.

Knight argued that uncertainty gave rise to economic profits that perfect competition could not eliminate.

Samuelson's most famous piece of work, Foundations of Economic Analysis (1947), one of the grand tomes that helped revive Neoclassical economics and launched the era of the mathematization of economics.

Giffen is credited by Marshall for suggesting the possibility that, in the case of some inferior goods, the income effects are so strong that the law of demand may be violated.