Based on a review and critique of extant literature on expertise we develop a model for describing the necessary requirements for experts’ ability to deal with unexpected situations. This model is rooted in the neo-pragmatist view on fallibilism, which both acknowledges the need for expertise and its limitations. In particular, experts’ practice is explained as the mapping of problem and solutions states (reality) to problem statements and solution statements (representation). To achieve this mapping, two types of knowledge are required: First, rules knowledge and domain specific expertise, and second, background knowledge and folk knowledge. While traditional views on expertise emphasize the first type of knowledge, we propose that the ability to deal with unexpected situations is especially dependent on the development of the second type of knowledge. We explain and discuss the model by referring to existing empirical examples.