Over the past fifteen years, a theoretical model and approach to cognitive neuropsychology (CNP) has emerged for understanding language disorders. The language processing model developed using the CNP approach provides a logical way of thinking about whether language processing is impaired, the level of impairment, and the cause of the impairment, and it helps us to analyze the root causes of the various clinical manifestations of aphasia. The CNP evaluation method is based on the cognitive neuropsychological hypothesis that the human language system is organized in a modular processing manner and that brain damage can selectively disrupt some modules while leaving others unaffected. Once it is determined which modules function normally and which are impaired, the speech therapist can develop a treatment plan to appropriately re-stock, reconstruct, or compensate for the impaired processing. The method provides a basic answer to aphasiology and, more importantly, it enables the therapist to make predictions as to what exactly is wrong with the patient and provides the rationale for treatment, and in turn the results of such interventions can further refine the model itself.