The paper discusses some of the 'belief systems knowledge' used in language understanding. It begins with a presentation of a theory of personal causation. The theory supplies the tools to account for purposeful behavior. Using primitives of the theory the social aspect of an action can be described. The social aspect is that which depends on beliefs and intentions. Patterns of behavior, called 'social action paradigms' (SAP's), are then defined in terms of social actions. The SAP's provide a structure for episodes analogous to the structure a grammar provides for sentences.