 Meanwhile, Friedman himself has extensively developed the idea of historically contingent but constitutive a prioris (e.g., 2001, 2003, 2008). He is sympathetic to Kuhn’s view that revolutions occur when the constitutive principles change. From the old point of view, there is disruptive and incommensurability, but defenders of the new viewpoint manages to establish a kind of continuity. Friedman goes well beyond Kuhn in stressing the role of philosophical ideas in establishing this continuity.