This paper claims that modern Contrastive Linguistics can be considered as a “double” interface between theory and application and between various linguistic approaches. It shows how empirical problems, hindering the original contrastive enterprise, led to the emergence of Error and Interlanguage analyses, which primarily focus on actual problems occurring in language acquisition and use the findings to solve them. One of the key questions is whether one can deal with learners’ errors in ignoring their L1. The paper carries out a historical outline demonstrating the interconnections between Contrastive Linguistics and Error/ Interlanguage Analyses and their individual limitations. Therefore, it argues that, despite their apparent opposition, they are rather complementary fields, with converging points and common goals to second or third language acquisition. The study also examines how corpus-based approach emerges as a converging empirical ground to these fields.