It has often been pointed out that the Marxian theory of value contains some inconsistencies, usually in relation to the concept of abstract labour. However, the contradiction between the concept of labour and the concept of validity with which Marx operates in Capital (without actually explaining this conception) has never been discussed. A detailed analysis shows that this concept of validity refers to the process of abstraction which is carried out by the participants of the exchange process. Only the rigorous comprehension of this process of abstraction can illuminate that for which the concept of abstract labour was developed: the unity and universality of value. On this basis, the paper criticises the Marxian development of the money-form and presents an alternative approach that builds on the aforementioned concept of validity. This concept is formulated in more depth by recourse to the works of Hegel, Simmel and Adorno. Furthermore, the paper reconsiders the dialectical development of categories in the light of this alternative conception of the money-form as totality and abstraction (in the sense of Hegel and the young Marx). Finally, the distinction between simple circulation and the process as a whole (found only in the Grundrisse) is explored and it is argued that, according to the novel reading proposed, it acquires a fundamental significance.