We describe a working example of mechanical default reasoning that is rather robust, in that it can detect a conflict between a default conclusion and another assertion (or conclusion), can (under suitable conditions) decide between them, and can maintain this decision indefinitely until overridden by information to do so. Our model contains five key elements: STM, LTM, ITM, QTM, and RTM. STM, LTM, and ITM are standard parts of cognitively- based models of memory. QTM is a technical device that controls the flow of information into STM, and RTM is the repository of default resolution and relevance.