A table, as a use-value, is just wood worked into a useful shape. But as a commodity, it suddenly becomes "a very queer thing, abounding in metaphysical subtleties and theological niceties." The queer thing about the commodity is that its exchange value appears to arise from the object itself — from the table's intrinsic properties — when in fact it expresses something entirely different: the quantity of socially necessary labour time congealed in its production. The social character of labour, which is the real basis of exchange, is hidden behind the apparently objective value of things.
Marx insists that commodity fetishism is not merely an error that could be corrected by education. It arises necessarily from the structure of capitalist production itself. In a society where production is carried out privately, by independent producers who only discover their social relations through the market exchange of their products, the social character of their labour can only appear in the form of the value-relation between commodities. The fetish character is the form in which private labour takes on a social character under capitalism — it would disappear only if production were organised on a directly social basis.
Commodity fetishism is the template for Marx's theory of ideology more broadly. Ideology is not merely false consciousness — it is not simply error that can be dispelled by argument. Rather, it is a form of thought that accurately reflects the surface appearance of capitalist social relations while concealing their underlying structure. The prices in a marketplace really do appear to be natural properties of commodities; the equality of exchange really does appear to be a basic fact about the market. To penetrate ideology requires going beyond appearances to the underlying social relations — which is what Capital, as a critique of political economy, attempts to do.
Commodity fetishism is introduced in the first chapter of Capital, Volume I (1867), in the section titled "The Fetishism of the Commodity and Its Secret." It is regarded by many interpreters as the philosophical heart of the entire work and as Marx's most original contribution to social theory.
