Classical economics is widely regarded as the first modern school of economic thought. Its major developers include Adam Smith, Jean-Baptiste Say, David Ricardo, Thomas Malthus and John Stuart Mill.
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.