Before the modern era, there was no formal, systematic economic thought. However, several ancient thinkers laid the groundwork for later economic reasoning.
Xenophon (c. 430–354 BC) wrote Oeconomicus — from which the word "economy" derives (οἶκος = household, νόμος = law) — and discussed the public finances of Athens. He analysed how to increase state revenue through trade and silver mining.
Plato (c. 428–348 BC) discussed the division of labour in The Republic, arguing that specialisation arises naturally because individuals differ in aptitude. He envisioned a society where each class performs its designated function.
Aristotle (384–322 BC) distinguished between oikonomia (household management, natural acquisition) and chrematistics (the art of money-making, potentially unnatural). He condemned usury — lending money at interest — as "the most hated sort" of wealth acquisition, because money was meant to be a medium of exchange, not to breed more money.
The Church Fathers (particularly St. Thomas Aquinas, 1225–1274) developed the doctrine of the just price (justum pretium) — the idea that goods should be exchanged at a price reflecting their true value, covering costs and a reasonable profit. Usury (charging interest on loans) was condemned as sinful.
Nicola d'Oresme (1323–1382), Bishop of Lisieux, wrote De Moneta (c. 1360), one of the earliest treatises on monetary theory. He articulated a commodity-money theory: money derives its value from the precious metal it contains. He argued against currency debasement by rulers and formulated what is now recognised as a precursor to Gresham's Law — that "bad money drives out good" when both circulate at the same face value.
Fra Luca Pacioli (1447–1517) published Summa de Arithmetica in 1492, which contained the first printed description of double-entry bookkeeping. This system — with its debits and credits, balance sheets and income statements — became the foundation of modern accounting and enabled the systematic tracking of business performance.
Mercantilism was the dominant economic doctrine in Europe from the 16th to the 18th century. It was not a unified theory but rather a collection of policies and beliefs shared by statesmen and merchants.
The central equation of mercantilist thought:
National Wealth = Accumulation of Gold and Silver
The mercantilist logic chain:
Governments actively intervened to ensure a favourable balance of trade:
Key mercantilist thinkers include Thomas Mun (1571–1641) in England, Jean-Baptiste Colbert (1619–1683) in France (Colbertism), and Antonio Serra (1580–?) in Italy.
The Physiocrats were a group of 18th-century French economists who mounted the first systematic challenge to mercantilism. The term derives from Greek: φύσις (nature) + κράτος (power) — "the rule of nature."
Quesnay, physician to Louis XV, was the founder of Physiocracy. His masterwork, the Tableau Économique (1758), was the first attempt to describe the economy as a circular flow — a system of interdependent sectors exchanging goods and money.
Quesnay divided society into three classes based on their economic role:
The Physiocrats introduced several ideas that proved enormously influential:
Classical economics, born in Britain in the late 18th century, established economics as a distinct discipline with systematic theoretical foundations.
Smith's An Inquiry into the Nature and Causes of the Wealth of Nations (1776) is widely considered the founding text of modern economics.
Key contributions:
Smith distinguished between use value (utility of an object) and exchange value (purchasing power). He noted the famous diamond-water paradox: water has enormous use value but low exchange value; diamonds have little use value but high exchange value. This paradox would remain unresolved until the Marginalist Revolution.
For Smith, the natural price of a commodity equals the sum of the natural rates of wages, profit, and rent required to bring it to market. The market price fluctuates around this natural price according to supply and demand.
Ricardo, a London stockbroker turned political economist, developed classical economics into a rigorous deductive system. His main work is On the Principles of Political Economy and Taxation (1817).
Ricardo's most enduring contribution. Even if one country is more efficient at producing everything, both countries benefit from trade if each specialises in what it produces at the lowest relative (opportunity) cost.
Classic example: England and Portugal both produce cloth and wine. Portugal is more efficient at both, but its advantage is greatest in wine. If Portugal specialises in wine and England in cloth, and they trade, both end up with more of both goods than under autarky.
The value of a commodity is determined (approximately) by the quantity of labour required to produce it. This includes both direct labour and the "embodied labour" in tools and machinery used. Ricardo acknowledged complications (different skill levels, capital intensity) but maintained labour as the primary determinant.
Wages tend toward the subsistence level: if wages rise above subsistence, population grows (more children survive), labour supply increases, and wages fall back. If wages fall below subsistence, population declines, labour becomes scarce, and wages rise. The long-run equilibrium is always at the minimum necessary to sustain the working population.
Rent arises because land differs in fertility. As population grows, less fertile land must be cultivated. The rent on better land equals the difference in productivity between that land and the worst (marginal) land in use, which pays no rent. Rent is thus a differential surplus, not a cost of production.
Marx built upon — and radically critiqued — the classical tradition, particularly Ricardo's labour theory of value. His magnum opus is Das Kapital (Volume I, 1867).
Marx's central economic concept. Workers sell their labour-power to capitalists. The value of labour-power equals subsistence (what it costs to reproduce the worker). But workers produce more value in a day than they receive in wages. The difference is surplus value — appropriated by the capitalist as profit.
If the working day is 10 hours, and the worker reproduces the value of their wages in 6 hours (necessary labour time), the remaining 4 hours constitute surplus labour time. The rate of exploitation:
\[ s' = \frac{\text{surplus value}}{\text{variable capital}} = \frac{s}{v} \]
For Marx, all history is the history of class struggle — between those who own the means of production and those who must sell their labour. The economic "base" (mode of production) determines the political and ideological "superstructure."
Historical materialism sees history progressing through stages:
Each transition occurs when the forces of production (technology, labour) outgrow the relations of production (property, social structure), generating contradictions that are resolved through revolution.
Marx predicted that capitalism contains the seeds of its own destruction. As capitalists compete, they substitute machines for workers (increasing the organic composition of capital). Since only living labour creates surplus value, the rate of profit tends to fall:
\[ r = \frac{s}{c + v} \]
where \(c\) = constant capital (machines, materials), \(v\) = variable capital (wages), \(s\) = surplus value. As \(c\) grows relative to \(v\), the denominator grows faster than the numerator.
In the early 1870s, three economists independently and almost simultaneously overturned the classical labour theory of value. This is one of the most remarkable cases of simultaneous discovery in the history of science.
The marginalists replaced the objective (labour-based) theory of value with a subjective one: the value of a good is determined by the utility of the last unit consumed — the marginal utility.
Law of diminishing marginal utility: each successive unit of a good yields less additional satisfaction than the previous one.
This elegantly resolves the diamond-water paradox: water is abundant, so its marginal utility is low (even though total utility is enormous). Diamonds are scarce, so their marginal utility is high. Price reflects marginal, not total, utility.
The consumer equilibrium condition — maximising utility subject to a budget constraint:
\[ \frac{MU_1}{P_1} = \frac{MU_2}{P_2} = \ldots = \frac{MU_n}{P_n} \]
where \(MU_i\) is the marginal utility of good \(i\) and \(P_i\) its price.
Walras developed the concept of general equilibrium: all markets in an economy are interconnected, and equilibrium must be achieved simultaneously in all of them. He described this through a system of simultaneous equations — one for each market — and argued that if \(n-1\) markets are in equilibrium, the \(n\)-th must be as well (Walras's Law).
Keynes revolutionised economics during the Great Depression with The General Theory of Employment, Interest and Money (1936), arguably the most influential economics book of the 20th century.
Critique of Say's Law: Classical economics held that "supply creates its own demand" (Say's Law) — that production automatically generates enough income to purchase all output. Keynes argued this is false: people may save rather than spend, creating a shortfall in aggregate demand.
Aggregate Demand determines the level of output and employment in the short run:
\[ Y = C + I + G + (X - M) \]
where \(Y\) = national income, \(C\) = consumption, \(I\) = investment, \(G\) = government spending, \(X\) = exports, \(M\) = imports.
An initial increase in spending (e.g., government investment) generates a multiplied increase in national income, because one person's spending becomes another's income:
\[ k = \frac{1}{1 - MPC} \]
where \(k\) is the multiplier and \(MPC\) is the marginal propensity to consume. If \(MPC = 0.8\), then \(k = 5\): every £1 of new government spending generates £5 of additional income.
Keynes argued that during recessions, the private sector alone cannot restore full employment. Government intervention is necessary:
The economy can settle at an equilibrium below full employment — involuntary unemployment is a real and persistent phenomenon, not a temporary aberration.
From the late 1960s onward, a counter-revolution challenged Keynesian dominance, led by Milton Friedman (1912–2006) and the Chicago School.
Core thesis: inflation is "always and everywhere a monetary phenomenon." The primary determinant of nominal GDP is the money supply, not fiscal policy.
The Quantity Theory of Money (revived from Irving Fisher):
\[ MV = PY \]
where \(M\) = money supply, \(V\) = velocity of money, \(P\) = price level, \(Y\) = real output. Friedman argued that \(V\) is stable and predictable, so changes in \(M\) directly affect \(PY\).
Key critiques of Keynesianism:
The Thatcher (UK, 1979–1990) and Reagan (US, 1981–1989) era implemented monetarist and free-market policies:
Contemporary economics has moved beyond the Keynesian-Monetarist divide toward a more eclectic, evidence-based discipline.
Provides microfoundations for Keynesian conclusions: price and wage stickiness, imperfect competition, and information asymmetries explain why markets don't clear instantly. Key figures: Gregory Mankiw, Joseph Stiglitz, Paul Krugman.
The standard New Keynesian model combines:
Challenges the assumption of perfect rationality. Pioneered by Daniel Kahneman and Amos Tversky (Prospect Theory, 1979), and developed by Richard Thaler (nudge theory). Key insights:
Emphasises the role of institutions — laws, norms, property rights, governance structures — in shaping economic outcomes. Key figures: Douglass North (Nobel 1993), Daron Acemoglu, James Robinson (Why Nations Fail, 2012).
Core argument: the difference between rich and poor nations is primarily explained by inclusive vs. extractive institutions, not geography, culture, or ignorance.
| Period | School | Key Figure(s) | Central Idea |
|---|---|---|---|
| Antiquity | Proto-economics | Aristotle, Xenophon | Household management, just exchange |
| XIV–XV c. | Scholastics | Oresme, Pacioli | Sound money, double-entry bookkeeping |
| XVI–XVII c. | Mercantilism | Mun, Colbert | Wealth = gold, trade surplus |
| XVIII c. | Physiocracy | Quesnay | Agriculture = only productive sector |
| 1776–1870 | Classical | Smith, Ricardo, Mill | Labour value, free markets, comparative advantage |
| 1867– | Marxism | Marx, Engels | Surplus value, class struggle |
| 1871– | Marginalism | Jevons, Menger, Walras | Marginal utility, general equilibrium |
| 1936– | Keynesianism | Keynes | Aggregate demand, multiplier, state intervention |
| 1960s– | Monetarism | Friedman | Money supply, natural rate, policy rules |
| 1990s– | Modern synthesis | Mankiw, Kahneman, Acemoglu | Microfoundations, bounded rationality, institutions |