ABSTRACT
The main theme of this chapter is reflected in the title. Brown, Heisenberg and Lorenz have contributed in an important way to the understanding of physical phenomena by showing that there are essential limitations to the accuracy of measurement and the predictability of physical events. The chapter has two parts. In the first part an account is given of the achievements and limitations of a century of psychological measurement and research, with an emphasis on the tendency of psychologists to over-generalize results. This is followed by an interlude in which the ideas of the three above-mentioned scientists are summarized. The brief second part indicates a possible way in which psychological measurement theory can be extended to approach the uncertainty and unpredictability that appear to be inherent in behaviour.
