This talk outlines a new research program that investigates the contributions that studies of linguistic microvariation (i.e. variation between closely related varieties of a single language) can make to linguistic theory, and, in particular, to the construction of theories of the semantic module of the grammar and the syntax-semantics interface. Since the 1960s, studies of dialectal, historical and sociolinguistic variation have made enormous empirical contributions to theories of the phonological and morphological components of the grammar; however, it is only relatively recently that syntactic microvariation phenomena have entered the domain of study of theoretical linguistics (cf. Vinet & Roberge (1989), Kroch (1989), Kayne (1996), among others). Furthermore, as observed by von Fintel and Matthewson (2008), up to this point, studies of dialectal, historical or sociolinguistic variation have not played a large role in the construction of formal semantic theories. Therefore, the main goal of the research program is to exploit the (as yet largely untapped) resource that are variation studies with the aim of advancing semantic theory. As a concrete illustration of this methodology, I present a diachronic study of the evolution of resultative secondary predication constructions (ex. to hammer the metal flat, or to float under the bridge (directional interpretation)) from Latin to Modern French, with a particular focus on the resultative system of Old and Middle French (11-14th centuries). I show how, using a series of quantitative corpus-based diachronic studies, we can test the predictions of current analyses in the theoretical literature concerning the compositional semantics and typological distribution of resultative constructions and, in doing so, arrive at a better understanding of the grammatical foundations of causal and telic interpretations in natural language.