Why New Schools of Economics Arise — and What Each One Changed

What Causes a New School to Form

An unexplained anomaly: A school gains ground when the dominant framework cannot account for something obvious — mass unemployment for the classicals, stagflation for the Keynesians, systematic experimental deviations for the rational-choice model.
A methodological opening: New tools make new questions tractable, as calculus enabled marginalism and, later, national accounts enabled macroeconomics.
A live policy dispute: The Corn Laws, the socialist calculation debate, and the choice between fiscal and monetary policy each pulled a school into existence around a concrete argument.
An institutional base: Schools consolidate around universities and journals — Cambridge for Marshall and Keynes, Chicago for Friedman and Lucas, Vienna for the Austrians.
Generational turnover: Ideas that are marginal when introduced often become mainstream only when a later cohort, less committed to the old framework, takes them up.

Classical: wealth redefined: National wealth became the flow of production rather than a hoard of bullion, which undercut mercantilism and armed the free-trade movement.
Classical: a systematic discipline: Political economy acquired a core set of questions — value, rent, wages, growth — and a deductive method that organised the field for decades.
Marxist: distribution and class: Marx forced the questions of exploitation, class conflict and the distribution of the surplus permanently onto the intellectual agenda, even for those who rejected his answers.
Marxist: crisis as normal: The idea that instability is a structural feature of capitalism, not an accident, entered economic and political argument and never left.
Both: they framed the alternatives: Later schools defined themselves partly by contrast with the labour theory of value that classical and Marxist economics shared.

Value relocated: Grounding value in marginal utility dissolved the water-diamond paradox and made the individual optimising agent the unit of analysis.
Mathematics normalised: Walras's general equilibrium made systems of simultaneous equations a standard tool rather than an eccentricity.
Micro foundations: The marginalist focus on individual choice is the origin of the later insistence that macroeconomics rest on explicit micro behaviour.
Austrian: the knowledge problem: The argument that prices coordinate dispersed information reframed the case for markets and shaped the socialist calculation debate.
Austrian: entrepreneurship and process: Emphasis on discovery and disequilibrium adjustment kept alive a view of markets as processes rather than as static equilibria.

Keynesian: macroeconomics itself: The systematic study of aggregate demand and output, and the justification for fiscal policy, both date from the General Theory.
Monetarist: the role of money: Monetarism returned money and the central bank to the centre of the inflation debate and discredited the idea that demand management alone controls prices.
New classical: expectations: Rational expectations forced every macro model to take seriously how people anticipate policy, changing what counted as a credible model.
New Keynesian: frictions with rigour: Sticky prices and imperfect competition, embedded in modern microfounded models, underpin much contemporary central-bank analysis.
Behavioural: the rationality assumption: Documented, systematic departures from rational choice reopened questions the whole edifice had assumed were settled.