In forging his theory of discourse in Language, Semantics and Ideology, Michel Pêcheux, based upon Paul Henry, refers to the relative autonomy of the linguistic system by proposing a distinction between linguistic base and discursive process. The autonomy of language (langue) is relative because, as Pêcheux points out, the separation between the linguistic base and the discursive process cannot be defined once and for all; it is subject to historical transformation through the return effect of discursive processes upon language (langue) itself. We argue here that the perspective outlined by Michel Pêcheux, according to which there is a distinction between a linguistic base (endowed with relative autonomy) and discursive processes (which exert a return effect upon the linguistic base), corresponds to a renewal of the Saussurean discussion on the relationship between the synchronic and diachronic points of view, according to which there is both autonomy and interdependence between synchrony and diachrony. The study thus points to an unexpected consonance between Pêcheux’s elaborations in Language, Semantics and Ideology and the Saussurean discussion on synchrony and diachrony, despite Pêcheux’s explicit critique of the Saussurean concept of parole (speech).