This chapter1 deals with the theoretical foundations of Balkan Sprachbund studies: their purpose and aims, terminology and methods, and the areal and intralinguistic evidence for the regularity of contact-induced Balkanization processes on the peninsula. Instead of deconstruction, Balkan Sprachbund theory is supported by positivism, historicism, structuralism, social relevance and sufficient field data. These together demonstrate that it is possible to acquire new and profound insights into linguistic convergence in general and to provide Balkan linguistics with paradigms for research and models of interpretation. The concepts of linguistic boundary, dialect, regular correspondences in the functions of linguistic units, parallel grammaticalization, lexicalization, and semantic neutralization are stressed as crucial for understanding the nature of linguistic and cultural convergence and divergence that may manage to either evade or intensify identity loss. I argue that a facts-on-the-ground-based Sprachbund theory is capable of making predictions on the basis of the regularity of linguistic convergence in the Balkans. It is further argued that, for the first time in Balkan linguistics, thorough attention is being paid to bilingual symbiotic groups in zones of ongoing intimate contact on the part of the language and speech behaviour of their members.