Metatheoretical and, more generally, methodological analyses of psychological problems and theories have a long tradition; however, their impact on scientific practice, especially on the clarification and testing of existing psychological theories and the formulation of new ones, has so far been less than spectacular. The increased interest in theoretical psychology visible during the past ten or twenty years is associated with the hope that a change of this situation will gradually be effected. Thus, in their preface to the proceedings of the founding conference of The International Society...

Some data-analytic methods excel by their sheer elegance. Their basic principles seem to have a particular attraction, based on a intricate combination of simplicity, deliberation, and power. They usually balance on the verge of two disciplines, data-analysis and foundational measurement, or statistics and psychology. To me, unfolding has always been one of them. The theory and the original methodology were created by Clyde Coombs (1912-1988) to describe and analyze preferential choice data. The fundamental assumptions are truly psy- chological; Unfolding is based on the notion of a single...