In his value-form theory, Marx employs the paired categories of use-value and value, concrete labor and abstract labor, individual labor and social labor, the value-substance and value-form, the equivalent form and the relative form in the conceptual transition from the commodity to money, integrating both social and quantitative aspects of value. Modern theories of value-form, claiming to "reconstruct" Marx's theory, tend to collapse these paired categories into mystified concepts of pure form without content, abstract money imposed from without, and understate or banish the quantitative aspect of Marx's theory. These writers have in fact constructed alternative theories different from Marx's. Marx's value-form theory also gives rise to certain logical implications on the current solutions to the transformation problem and points to further studies on the capital-form and capitalist crises