Abstract
In a recent exchange, John Worrall and Larry Laudan have debated the merits of the model of rational scientific change proposed by Laudan in his book Science and Values. On the model advocated by Laudan, rational change may take place at the level of scientific theory and methodology, as well as at the level of the epistemic aims of science. Moreover, the rationality of a change which occurs at any one of these three levels may be dependent on considerations at the remaining levels. Yet, in spite of the avowedly anti-relativistic motivation of Laudan's model, Worrall criticizes Laudan for irrevocably relativizing scientific rationality to historically variant methodological standards.