 Given that cyclic theories of history have, for the most part, long given way to linear, progressive accounts, readers may be surprised at Kuhn critic, physicist Stephen Weinberg’s comment that Kuhn’s overall model is still, in a sense, cyclic (Weinberg 2001). In fact, Kuhn himself had already recognized this. After the founding paradigm in Kuhn’s account in Structure, we have normal science under a paradigm, then crisis, then revolution, then a new paradigm—a development that brings back a new period of normal science. At this abstract level of description, the model is indeed cyclic, but of course the new paradigm heads the science in question in a new direction rather than returning it to a previous state. Other commentators, including Marxists, have regarded Kuhn’s mechanism as dialectical, as illustrated by the succession of self-undermining developments in the theory of light, from a Newtonian particle theory to a wave theory to a new kind of wave-particle duality. (For the dialectical interpretation see especially Krajewski 1977 and Nowak 1980 on the idealizational approach to science, as originated by Karl Marx.)