Adam Smith's The Wealth of Nations in 1776 is usually considered to mark the beginning of classical economics. The school was active into the mid 19th century and was followed by neoclassical economics in Britain beginning around 1870, or, in Marx's definition by "vulgar political economy" from the 1830s. The definition of classical economics is debated, particularly the period 1830–70 and the connection to neoclassical economics. The term "classical economics" was coined by Karl Marx to refer to Ricardian economics – the economics of David Ricardo and James Mill and their predecessors – but usage was subsequently extended to include the followers of Ricardo.
Classical economists claimed that free markets regulate themselves, when free of any intervention. Adam Smith referred to a so-called invisible hand, which will move markets towards their natural equilibrium, without requiring any outside intervention.
As opposed to Keynesian economics, classical economics assumes flexible prices both in the case of goods and wages. Another main assumption is based on Say's Law: supply creates its own demand - that is, aggregate production will generate an income enough to purchase all the output produced; this implicitly assumes, in contrast to Keynes, that there will be net saving or spending of cash or financial instruments. Another postulate of classical economics is the equality of savings and investment, assuming that flexible interest rates will always maintain equilibrium.
The classical economists produced their "magnificent dynamics" during a period in which capitalism was emerging from feudalism and in which the industrial revolution was leading to vast changes in society. These changes raised the question of how a society could be organized around a system in which every individual sought his or her own (monetary) gain. Classical political economy is popularly associated with the idea that free markets can regulate themselves.
Classical economists and their immediate predecessors reoriented economics away from an analysis of the ruler's personal interests to broader national interests. Adam Smith, and also physiocrat Francois Quesnay, for example, identified the wealth of a nation with the yearly national income, instead of the king's treasury. Smith saw this income as produced by labour, land, and capital. With property rights to land and capital held by individuals, the national income is divided up between labourers, landlords, and capitalists in the form of wages, rent, and interest or profits.
Modern legacy 
Classical economics is generally agreed (but see section Debates on the definition of classical economics below) to have developed into neoclassical economics – as the name suggests – or to at least be most closely represented in the modern age by neoclassical economics, and many of its ideas remain fundamental in economics. Other ideas, however, have either disappeared from neoclassical discourse or been replaced by Keynesian economics in the Keynesian revolution and neoclassical synthesis. Some classical ideas are represented in various schools of heterodox economics, notably Marxian economics – Marx being a contemporary of the classical economists and their immediate successors – and Austrian economics, which split from neoclassical economics in the late 19th century.
Classical theories of growth and development 
Analyzing the growth in the wealth of nations and advocating policies to promote such growth was a major focus of classical economists. John Hicks & Samuel Hollander, Nicholas Kaldor, Luigi L. Pasinetti, and Paul A. Samuelson have presented formal models as part of their respective interpretations of classical political economy.
Value theory 
Classical economists developed a theory of value, or price, to investigate economic dynamics. William Petty introduced a fundamental distinction between market price and natural price to facilitate the portrayal of regularities in prices. Market prices are jostled by many transient influences that are difficult to theorize about at any abstract level. Natural prices, according to Petty, Smith, and Ricardo, for example, capture systematic and persistent forces operating at a point in time. Market prices always tend toward natural prices in a process that Smith described as somewhat similar to gravitational attraction.
The theory of what determined natural prices varied within the Classical school. Petty tried to develop a par between land and labour and had what might be called a land-and-labour theory of value. Smith confined the labour theory of value to a mythical pre-capitalist past. Others may interpret Smith to have believed in value as derived from labour. He stated that natural prices were the sum of natural rates of wages, profits (including interest on capital and wages of superintendence) and rent. Ricardo also had what might be described as a cost of production theory of value. He criticized Smith for describing rent as price-determining, instead of price-determined, and saw the labour theory of value as a good approximation.
- The level of outputs at the level of Smith's "effectual demand",
- technology, and
From these givens, one can rigorously derive a theory of value. But neither Ricardo nor Marx, the most rigorous investigators of the theory of value during the Classical period, developed this theory fully. Those who reconstruct the theory of value in this manner see the determinants of natural prices as being explained by the Classical economists from within the theory of economics, albeit at a lower level of abstraction. For example, the theory of wages was closely connected to the theory of population. The Classical economists took the theory of the determinants of the level and growth of population as part of Political Economy. Since then, the theory of population has been seen as part of Demography. In contrast to the Classical theory, the determinants of the neoclassical theory value:
- technology, and
are seen as exogenous to neoclassical economics.
Classical economics tended to stress the benefits of trade. Its theory of value was largely displaced by marginalist schools of thought which sees "use value" as deriving from the marginal utility that consumers finds in a good, and "exchange value" (i.e. natural price) as determined by the marginal opportunity- or disutility-cost of the inputs that make up the product. Ironically, considering the attachment of many classical economists to the free market, the largest school of economic thought that still adheres to classical form is the Marxian school.
Monetary theory 
British classical economists in the 19th century had a well-developed controversy between the Banking and the Currency school. This parallels recent debates between proponents of the theory of endogeneous money, such as Nicholas Kaldor, and monetarists, such as Milton Friedman. Monetarists and members of the currency school argued that banks can and should control the supply of money. According to their theories, inflation is caused by banks issuing an excessive supply of money. According to proponents of the theory of endogenous money, the supply of money automatically adjusts to the demand, and banks can only control the terms (e.g., the rate of interest) on which loans are made .
Debates on the definition of classical economics 
The theory of value is currently a contested subject. One issue is whether classical economics is a forerunner of neoclassical economics or a school of thought that had a distinct theory of value, distribution, and growth.
Sraffians, who emphasize the discontinuity thesis, see classical economics as extending from Petty's work in the 17th century to the break-up of the Ricardian system around 1830. The period between 1830 and the 1870s would then be dominated by "vulgar political economy", as Karl Marx characterized it. Sraffians argue that: the wages fund theory; Senior's abstinence theory of interest, which puts the return to capital on the same level as returns to land and labour; the explanation of equilibrium prices by well-behaved supply and demand functions; and Say's law, are not necessary or essential elements of the classical theory of value and distribution.
Perhaps Schumpeter's view that John Stuart Mill put forth a half-way house between classical and neoclassical economics is consistent with this view.
Sraffians generally see Marx as having rediscovered and restated the logic of classical economics, albeit for his own purposes. Others, such as Schumpeter, think of Marx as a follower of Ricardo. Even Samuel Hollander has recently explained that there is a textual basis in the classical economists for Marx's reading, although he does argue that it is an extremely narrow set of texts.
Another position is that neoclassical economics is essentially continuous with classical economics. To scholars promoting this view, there is no hard and fast line between classical and neoclassical economics. There may be shifts of emphasis, such as between the long run and the short run and between supply and demand, but the neoclassical concepts are to be found confused or in embryo in classical economics. To these economists, there is only one theory of value and distribution. Alfred Marshall is a well-known promoter of this view. Samuel Hollander is probably its best current proponent.
Still another position sees two threads simultaneously being developed in classical economics. In this view, neoclassical economics is a development of certain exoteric (popular) views in Adam Smith. Ricardo was a sport, developing certain esoteric (known by only the select) views in Adam Smith. This view can be found in W. Stanley Jevons, who referred to Ricardo as something like "that able, but wrong-headed man" who put economics on the "wrong track". One can also find this view in Maurice Dobb's Theories of Value and Distribution Since Adam Smith: Ideology and Economic Theory (1973), as well as in Karl Marx's Theories of Surplus Value.
The above does not exhaust the possibilities. John Maynard Keynes thought of classical economics as starting with Ricardo and being ended by the publication of Keynes' own General Theory of Employment Interest and Money. The defining criterion of classical economics, on this view, is Say's law which is disputed by Keynesian economics.
One difficulty in these debates is that the participants are frequently arguing about whether there is a non-neoclassical theory that should be reconstructed and applied today to describe capitalist economies. Some, such as Terry Peach, see classical economics as of antiquarian interest.
Sometimes the definition of classical economics is expanded to include the earlier 17th century English economist William Petty and the contemporary early 19th century German economist Johann Heinrich von Thünen.
See also 
- Classical general equilibrium model
- Neoclassical economics
- Classical liberalism
- Constitutional economics
- Perspectives on Capitalism
- The General Theory of Employment, Interest and Money, John Maynard Keynes, Chapter 1, Footnote 1
- Baumol, William J. (1970) Economic Dynamics, 3rd edition, Macmillan (as cited in Caravale, Giovanni A. and Domenico A. Tosato (1980) Ricardo and the Theory of Value, Distribution and Growth, Routledge & Kegan Paul)
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