[Uneasiness with facet analysis: time for a reappraisal].

Although already several decades old, the facet analysis (also called facet theory) has not been able to assert itself in the field of psychology. Here the reasons for the widespread uneasiness with the facet analysis will be presented starting with an outline of the approach. This will make it clear that the facet analysis does not represent a research method in the narrower sense and definitely not a "theory" but a method with the status of a logical principle of thought. In experimental psychology this principle has been used successfully for a long time in the form of multifactorial experimental designs. However, multifactorial measurement designs are still few and far between in differential and diagnostic psychology. This can be explained especially by the fact that an important aspect of validity--the validity of construct differentiations--has been ignored. Because of a principle rejection of factor analytic methods, even the proponents of the facet analysis have overlooked the central contribution of their approach with respect to the validity of measurement methods.