Discerning between science and "pseudoscience" was the theme of a book by Karl Popper whose summary was quoted in Daubert: "the criterion of the scientific status of a theory is its falsifiability, or refutability, or testability." The book, "Conjectures and Refutations: The Growth of Scientific Knowledge" (5th ed. 1989), pp. 34–57, explains how psychology is more like astrology than astronomy because it does not make predictions about an individual which are falsifiable. He wrote that "the impressive thing about" Einstein's predictions "is the risk involved...If observation shows that the predicted effect is definitely absent, then the theory is simply refuted." But "it was impossible to describe a human behaviour" which would be accepted as proving psychology false.