This article revisits the debates on socially necessary labor-time (SNLT) in the light of contemporary discussions of Marx´s value-theory, which have tended to move from a rather narrow focus on the explanation of the economic basis of the exploitation of wage-workers, to a wider critical inquiry into the social constitution of alienated forms of mediation that structure capitalist society. Moreover, this re-examination of SNLT draws on a novel reading of the textual evidence offered by the critical edition of the manuscripts for Capital, against the backdrop of a brief overview of the controversies between the three main interpretations which can be found in the literature, and the development of an alternative systematic-dialectical presentation of the constitution of the content and concrete forms of realization of the quantitative determination of value.