In discussing the form of prices in various draft manuscripts and in Das Kapital, Marx drew an essential distinction between actual prices charged and paid, i.e., prices that express how much money really changed hands, and various "ideal prices" (imaginary or notional prices).^[101]

Because prices are symbols or indicators in more or l

Value relationships among physical products or labour-services and physical assets — as proportions of current labour effort involved in making them — exist according to Marx quite independently from price information, and prices can oscillate in all sorts of ways around economic values, or indeed quite independently of them. However, the expression of product-value by prices in money-units in most cases does not diverge very greatly from the actual value; if there was a very big difference, people would not be able to sell them (insufficient income), or they would not buy them (too expensive, relative to other options).

If prices for products rise, hours worked may rise, and if prices fall, hours worked may fall (sometimes the reverse may also occur, to the extent that extra hours are worked, to compensate for lower income resulting from lower prices, or if more sales occur because prices are lowered). In that sense, it is certainly true that product-prices and product-values mutually influence each other. It is just that, according to Marx, product-values are not determined by the labor-efforts of any particular enterprise, but by the combined result of all of them.^[100]

In discussing the form of prices in various draft manuscripts and in Das Kapital, Marx drew an essential distinction between actual prices charged and paid, i.e., prices that express how much money really changed hands, and various "ideal prices" (imaginary or notional prices).^[101]

Because prices are symbols or indicators in more or less the same way as traffic lights are, they can symbolize something that really exists (e.g., hard cash) but they can also symbolize something that doesn't exist, or symbolize other symbols. The concept of price is often used in a very loose sense to refer to all kinds of transactional possibilities. That can make the forms of prices highly variegated, flexible and complex to understand, but also potentially very deceptive, disguising the real relationships involved.

Modern economics is

Because prices are symbols or indicators in more or less the same way as traffic lights are, they can symbolize something that really exists (e.g., hard cash) but they can also symbolize something that doesn't exist, or symbolize other symbols. The concept of price is often used in a very loose sense to refer to all kinds of transactional possibilities. That can make the forms of prices highly variegated, flexible and complex to understand, but also potentially very deceptive, disguising the real relationships involved.

Modern economics is largely a "price science" (a science of "price behaviour"), in which economists attempt to analyze, explain and predict the relationships between different kinds of prices—using the laws of supply and demand as a guiding principle. These prices are mostly just numbers, where the numbers are believed to represent real prices, in some way, as an idealization. Mathematics then provides a logical language, to talk about what these prices might do, and to calculate pricing effects. This however was not Marx's primary concern; he focused rather on the structure and dynamics of the capitalism as a social system. His concern was with the overall results that market activity would lead to in human society.

In what Marx called "vulgar economics", the complexity of the concept of prices is ignored however, because, Marx claimed in Theories of Surplus Value and other writings, the vulgar economists assumed that:

In his critique of political economy, Marx denied that any of these assumptions were scientifically true (see further real prices and ideal prices). He distinguished carefully between the values, exchange values, market values, market prices and prices of production of commodities.^[102]

However, he did not analyze all the different forms that prices can take (for example, market-driven prices, administered prices, accounting prices, negotiated and fixed prices, estimated prices, nominal prices, or inflation-adjusted prices) focusing mainly on the value proportions he thought to be central to the functioning of the capitalist mode of production as a social system. The effect of this omission was that debates about the relevance of Marx's value theory became confused, and that Marxists repeated the same ideas which Marx himself had rejected as "vulgar economics". In other words, they accepted a vulgar concept of price.^[103] Koray Çalışkan comments: "A mysterious certainty dominates our lives in late capitalist modernity: the price. Not a single day passes without learning, making, and taking it. Yet despite prices’ widespread presence around us, we do not know much about them."^[104]

Fluctuating price signals serve to adjust product-values and labour efforts to each other, in an approximate

However, he did not analyze all the different forms that prices can take (for example, market-driven prices, administered prices, accounting prices, negotiated and fixed prices, estimated prices, nominal prices, or inflation-adjusted prices) focusing mainly on the value proportions he thought to be central to the functioning of the capitalist mode of production as a social system. The effect of this omission was that debates about the relevance of Marx's value theory became confused, and that Marxists repeated the same ideas which Marx himself had rejected as "vulgar economics". In other words, they accepted a vulgar concept of price.^[103] Koray Çalışkan comments: "A mysterious certainty dominates our lives in late capitalist modernity: the price. Not a single day passes without learning, making, and taking it. Yet despite prices’ widespread presence around us, we do not know much about them."^[104]

Fluctuating price signals serve to adjust product-values and labour efforts to each other, in an approximate way; prices are mediators in this sense. But that which mediates should not be confused with what is mediated. Thus, if the observable price-relationships are simply taken at face value, they might at best create a distorted picture, and at worst a totally false picture of the economic activity to which they refer. At the surface, price aggregations might quantitatively express an economic relationship in the simplest way, but in the process they might abstract away from other features of the economic relationship that are also very essential to know.^[105] Indeed, that is another important reason why Marx's analysis of economic value largely disregards the intricacies of price fluctuations; it seeks to discover the real economic movement behind the price fluctuations.

Marx borrowed the idea of the form of value from the Greek philosopher Aristotle (circa 384-322 BC), who pondered the nature of exchange value in chapter 5 of Book 5 in his Nicomachean Ethics.^[106] Aristotle distinguished clearly between the concepts of use-value and exchange-value (a distinction taken over by Adam Smith). Aristotle developed a fairly sophisticated theory of money, and in chapter 9 of Book 1 of his Politics, he describes the circuits of commodity trade C-M-C' (oekonomia) and M-C-M' (chrematistikon).^[107] However, Marx criticized and developed Aristotle's ideas in an original way.^[108]

In so doing, Marx was also influenced by, and responding to, the "classical" political economy discourse about the economic laws governing commodity values and money,^[109] in Europe beginning (in Marx's view) with William Petty's Quantulumcunque Concerning Money (1682),^[110] reaching a high point in Adam Smith's An Inquiry into the Nature and Causes of the Wealth of N

In so doing, Marx was also influenced by, and responding to, the "classical" political economy discourse about the economic laws governing commodity values and money,^[109] in Europe beginning (in Marx's view) with William Petty's Quantulumcunque Concerning Money (1682),^[110] reaching a high point in Adam Smith's An Inquiry into the Nature and Causes of the Wealth of Nations (1776) and culminating with David Ricardo's Principles of Political Economy and Taxation (1817).^[111]

In particular, Marx's ideas about the forms of value were influenced by Samuel Bailey's criticism of Ricardo's theory of value.^[112] In Capital, Volume I, Marx stated that Bailey was one of the few political economists who had concerned themselves with the analysis of the form of value.^[113] Yet, Marx said, none of the political economists had understood its meaning, because they confused "the form of value" with "value itself", and because they only paid attention to the quantitative side of the phenomenon, not to the qualitative side.^[114] In Capital, Volume II, Marx criticizes Bailey again for "his general misunderstanding, according to which exchange-value equals value, the form of value is value itself", leading to the mistaken belief that "commodity values cease to be comparable once they no longer actively function as exchange-values, and cannot actually be exchanged for one another".^[115]

According to Marx, Aristotle already described the basics of the form of value when he argued^[116] that an expression such as "5 beds = 1 house" does not differ from "5 beds = such and such an amount of money", but according to Marx, Aristotle's analysis "suffered shipwreck" because he lacked a clear concept of value. By this Marx meant that Aristotle was unable to clarify the substance of value, i.e., what exactly was being equated in the value-comparisons when the relative worth of different goods is valued, or what was the common denominator commensurating a plethora of different goods for trading purposes.^[117] Aristotle thought the common factor must simply be the demand or need for goods, since without demand for goods that could satisfy some need or want, they would not be exchanged.

According to Marx, the substance of product-value is human labour-time in general, labour-in-the-abstract or "abstract labour". This value (an average current replacement cost in labour-time, based on the normal productivity of producers existing at the time) exists as an attribute of the products of human labour quite independently of the particular forms that exchange may take, though obviously value is always expressed in some form or other. It is perhaps not a very interesting insight if we consider only one commodity, but it is of much more interest when we face a huge variety of commodities which are all being traded, at the same time.

Marx's value-form idea can be traced back to his 1857 Grundrisse manuscript,^[118] where he contrasted communal production with production for exchange.^[119] Some humanist Marxists think the origin of the idea really goes further back in time, to Marx's 1844 Paris manuscripts, specifically the section on "the power of money"^[120] where Marx analyzes excerpts on money in Goethe's play Faust and Shakespeare's play Timon of Athens.^[121]

Marx felt that the playwrights had expressed the social meaning of money very well, and he discusses the magical power of money: why money can create a "topsy-turvy world" (verkehrte Welt) which unites opposites, fools people, or turns things into their contrary. However this textual interpretation is rejected by Althusserian