The aim is to problematize the concept of knowledge and the question of what constitutes scientific evidence. The comprehension of epistemology and the mistakes of science are discussed offering some ideas of the application and extent of evidence-based nursing, including the consequences for clinical nursing practice and research. This concerns both epistemological questions and how evidence is understood and must be understood.

The best treatment of the individual patient in the concrete situation cannot always be based on meta-analyses of clinically controlled tests. Some health science issues and problems are dependent on time, space and context, and they demand a concept of knowledge and research approach of another character than the traditional biomedical approach.