On the nature of subjective scales

A number of problems connected with psychophysical scaling are pointed out and solutions suggested. The importance of searching for invariant relations ("laws") is stressed and the advantage of dealing with intrasubjective relations—thereby avoiding the "physicalistic trap"—is emphasized. Two series of experiments, concerning time perception and similarity, are discussed and it is concluded that they support the validity of subjective scales. Finally the role of the observer in scaling experiments is commented on.