The General Theory of Employment, Interest and Money was written by the English economist John Maynard Keynes. The book, generally considered to be his magnum opus, is largely credited with creating the terminology and shape of modern macroeconomics. Published in February 1936, it sought to bring about a revolution, commonly referred to as the "Keynesian Revolution", in the way economists thought – especially in relation to the proposition that a market economy tends naturally to restore itself to full employment after temporary shocks. Regarded widely as the cornerstone of Keynesian thought, the book challenged the established classical economics and introduced important concepts such as the consumption function, the multiplier, the marginal efficiency of capital, the principle of effective demand and liquidity preference. The central argument of The General Theory is that the level of employment is determined, not by the price of labour as in neoclassical economics, but by the spending of money (aggregate demand). Keynes argues that it is wrong to assume that competitive markets will in the long run deliver full employment or that full employment is the natural, self-righting, equilibrium state of a monetary economy. On the contrary, under-employment and under-investment are likely to be the natural state unless active measures are taken. One implication of The General Theory is that an absence of competition is not the main issue regarding unemployment, and that even reducing wages or benefits have no major effect.