Thomas Kuhn upset both scientists and philosophers of science when he argued that transitions from one scientific framework (or “paradigm”) to another were irrational: the change was like a religious conversion experience rather than a reasoned shift from one theory to another based on the best evidence. But even if one disagrees with Kuhn, how can this change be shown to be rational? More generally, how can transitions from one set of normative standards to another be rational, given that there is no neutral position from which to criticize one’s own normative standards? In Creatively Undecided: Toward a History and Philosophy of Scientific Agency (University of Chicago Press, 2017), Menachem Fisch takes up this challenge, defending an account of framework change which accepts that we cannot be self-critical of our own standards, but we can be destabilized by external criticism. Some of those who are “ambivalated” in this way creatively attempt to tackle their ambivalence by developing hybrid theories that provide others in a scientific community with a means to critically assess their frameworks and develop new ones. Fisch, who is Professor of History and Philosophy of Science at Tel Aviv University, draws on work from Korsgaard, Friedman, Galison, McDowell and others in a rich discussion of the dynamics of normativity in science, illustrated with a case study of debates on the foundations of algebra in the 1830s.