There are five main lines of scholarly criticism of Marx's idea of the form of value.
Obscurantism
The criticism most often heard from the critics of Marx, such as Friedrich von Hayek, Karl Popper, Francis Wheen and Ian Steedman is that, even if Marx himself meant well, Marx's value-form idea is simply an esoteric obscurantism, "dialectical hocus pocus", "sophistry", or "mumbo jumbo". Francis Wheen refers to "a shaggy-dog story, a picaresque journey through the realms of higher nonsense." Mark Blaug stated that "the reader will miss little by skipping the pedantic third section of Chapter I".
This type of criticism was already being made while Marx was still alive, as Marx himself reports in a postface to the second German edition of Capital, Volume I in 1873.
Often, Marxists have replied to this type of criticism by restating Marx's arguments in clearer language, or by showing that Marx's theory of economic value at the very least fares no worse than the subjective theory of value (the theory of the util as the measuring unit of exchange).
Even so, when he published his very clear restatement Karl Marx's Theory of History: A Defence, the Analytic Marxist philosopher Gerald Cohen explicitly dissociated himself from Marx's value theory. Cohen argued that it is possible to have a historical materialism without a labour theory of value, because the one does not logically entail the other as well. Marcel van der Linden accepted Cohen's approach, noting that "whether Marx's theory is exactly right or not, it remains a fact that the working class produces a surplus product about which it has no say." Marx himself never referred to his own theory of value as a "labour theory of value" even once.
This interpretation contrasts with Lenin's opinion in 1894 — repeated by Johann Witt-Hansen—that with the appearance of Das Kapital, "the materialist conception of history is no longer a hypothesis, but a scientifically proven proposition". Earlier on, in 1880, Engels had written (at the end of Part 2 of his pamphlet Socialism: Utopian and Scientific) that "two great discoveries, the materialistic conception of history and the revelation of the secret of capitalistic production through surplus-value, we owe to Marx. With these discoveries, Socialism became a science."
Substance of value
Marx's argument is that the exchangeability of commodities with recognition of their value is enabled by the common factor that all of them are products of social labour (co-operative human labour producing things for others). Critics suggest that Marx's observations fail to provide any logically decisive proof that human labour-time (work effort) is the substance of the economic value of all products.
Marx's own response
In a famous letter from Marx to Ludwig Kugelmann dated 11 July 1868, Marx became extremely indignant and derisive about this objection, stating among other things that:
Modern debate
In 1989, Simon Clarke captured the essence of the modern value-form debate within Western Marxism, as a hyper-abstract scholastic debate about the form and content of economic value:
The unresolved issue, David Kristjanson-Gural commented, is that "If exchange effects the reduction of concrete to abstract labor, then the magnitude of value is determined not by the expenditure of labor in production, but only in exchange." Although Rubin did refer to "a quantitative determination of abstract labor before the act of exchange and independent of it", by his own definition he lacked any method for determining the magnitude of abstract labour prior to exchange, or for showing how it might influence product-values. Paradoxically, it seemed that if value itself can only be determined with reference to exchange ratios in markets, then value cannot be the sole determinant of prices (a conclusion already reached by Joan Robinson in 1950.)