Keynes's critique mainly argues against the barter or real exchange economy of the Classical School. He goes beyond the traditional argument of whether money is neutral or not and emphasises that money has to be regarded as an operational factor, which influences the economic motives and decisions of individuals. In this 'Monetary Theory of Production', he specifically argues against Alfred Marshall's Principles, where money is used as an important but ultimately neutral medium to determine the economy's barter exchange relations or the relative prices of goods. The Classical School define them as the decisive factors for economic activity. Instead, Keynes emphasises that statements about the barter economy are not necessarily transferable to the monetary economy. Despite this, he does not intend a total break from classical and neoclassical theory but aims to complete the barter theory the Classical School. Keynes interprets that school, as a specific case of his General Theory which only deals with the unusual state of full employment. A general theory of the economy should also analyse phenomena such as business cycles, crises, and unemployment in which money and interest are important factors.