For some years various fields of research, especially in education, have been concentrating on mistakes and their function in learning processes (e.g. Oser/Spychiger 2005). These efforts have resulted in different concepts about dealing with mistakes in lessons to help students learn from them (e.g. Caspary 2008). However an adequate explanation of how learning from mistakes exactly takes places has not been found, yet. The presentation intends to give insight into an approach focusing on how to close that gap by developing an error theory in terms of inferential processes. Therefore the notions of “error” in general as well as its different types are systematically investigated. Combining these steps with analyzing various causes of errors and their processing in reasoning could help to shed light on the mechanisms of learning - or not learning - from mistakes. The theoretical framework is based on a broadly constructivist paradigm of learning on the one hand (see Spychiger 2006) and an inferential theory of learning on the other hand (p.e. Minnameier 2005), that generally allows a localization of mistakes in learning processes.