This chapter presents examples of theoretical models of language function developed in the philosophy of language and psycholinguistics that are used both for the clinical diagnosis and therapy of language-impaired patients and for the design of neurolinguistic laboratory experiments. Neuroscientific research is initially exploratory and descriptive, but neurolinguistics experiments cannot be designed without a theoretical context. As in all scientific disciplines, neurolinguistic research questions are based on fundamental assumptions that enable concrete cognitive and neuroscientific hypotheses. Only this model theoretical embedding of neurolinguistics makes laboratory research possible, but at the same time limits the possible scope of knowledge. For example, holistic or modular cognition models, assumptions about bottom-up or top-down processing or the concept of embodied cognition are presented. Furthermore, models of the mental structure of cognition as well as important processing mechanisms such as interactive, serial or parallel processing steps of cognition are introduced, all of which are part of the model-theoretical basis of neurolinguistics.