It is proposed that humans have available to them two systems for interpreting natural language. One system is familiar from formal semantics. It is a type based system that pairs a syntactic form with its interpretation using grammatical rules of composition. This system delivers both plausible and implausible meanings. The other proposed system is one that uses the grammar together with knowledge of how the human production system works. It is token based and only delivers plausible meanings, including meanings based on a repaired input when the input might have been produced as a speech error.