Conceptual views on quality of life.
Quality of life can be discussed in many ways. One way is to analyse the empirical quantitative approach to determine whether the research categories are operational, empirically unambiguous, and thematically relevant; progress, in the sense of changing the number of research categories, does not take place through a systematic empirical test but through a modification of the theory of quality of life. The current debate on quality of life has included a conflict between natural science and a humanistic approach. Our view is that quality of life must be defined through the difficult concept of happiness. When cancer threatens happiness, not one but two fundamental crises influence quality of life, which we regard as a key concept of a therapeutic method.