The paper will start with an epistemological outline of the role of functional explanation in Natural Phonology, with emphasis on the semiotic, cognitive and phonetic bases of phonology. Natural Phonology is a theory of preferences rather than of constraints. Support for preferences comes from both internal and external (substantial) evidence for which illustrations will be provided from phonostylistics, diachrony and acquisition. For such areas bridge theories are needed, e.g., a bridge theory from the model of Natural Phonology to acquisitional constructivism which enables one to account for  first and second language acquisition data. In phonology, one realization of preferences is by means of functionally motivated phonological processes which must be distinguished from allomorphic and morphonological rules. The latter derive diachronically from phonological processes due to interactions with morphology. Such interactions also explain many cases of superheavy syllables and word final consonant clusters. Processes operate on representations which are, in principle, fully pronounceable. This principle disallows segmental underspecification and empty inputs. Processes respond both to paradigmatic and syntagmatic structural requirements. As a result, inventories and lexical representations emerge which are, in turn, input to further – postlexical – processes. Phonotactic preferences dictate the syntagmatic relationships between and among segments on the lexical and postlexical level.