The main tenet of this article is that Spanish philologist Ramón Menéndez Pidal’s (1869–1968) theoretical approach to the history of the language, as developed in his Manual de gramática histórica española (1904) and in Orígenes del español (1926), was a result not only of a highly original interpretation of the linguistic theories available to him and a need to improve their explanatory power, but also from an interplay between this theory and the ideological context from which it emerged. This ideological context, which I maintain is critical for the understanding of the full implications of Menéndez Pidal’s linguistic approach, has been assumed by traditional historiography to be outside the scope of linguistics. It is claimed here that the Spanish philologist’s scholarly accomplishments, justly praised by his disciples and hispanists in general, did not occur in a social vacuum, but were instead well entrenched in a specific intellectual, social, and historical context. Menéndez Pidal lived and worked in a period in which Spain, like other 19th-century liberal democracies, was building its identity as a nation-state. In this period, the construction of the Spanish nation was threatened by centrifugal forces (e.g., the articulation of Basque, Catalan, and Galician nationalisms) that challenged Spain’s unitary political and cultural identity. It is precisely against the backdrop of this socio-political landscape that Menéndez Pidal’s use of the neogrammarian model of convergence in the Manual, his scrupulous philological examination of old documents in Orígenes is interpreted – which, for him, offered proof of Castile’s destiny as the leading force in the history of Spain, including his integrative reworking of the phonetic law converting it into a means by which to perceive the unity underlying dialectal variation.