 Bachelard, French physicist and philosopher-historian of science, also believed that only by studying history of science can we gain an adequate understanding of human reason. He stressed the importance of epistemological breaks or discontinuities (coupures épistémologiques). In Le Nouvel Esprit Scientifique (1934), Bachelard argued that the worldview of classical physics, valuable in its own time, eventually became an obstacle to future progress in physics. Hence a break was needed. Here, then, we already find the idea that a successful theory can lose its luster by being considered exhausted of its resources and thus lacking in fertility. Like Brunschvicg, Bachelard held that a defensible, realist philosophy had to be based on the science of its day. Hence, scientific revolutions have (and ought to have) brought about epistemological revolutions. The reality we posit, he said, ought to be that of the best science but with the realization that our concepts are active constructs of our own minds, not imported from nature’s own language, as it were. Future mental activity as well as future empirical findings are likely to require another rupture. As Gutting points out, Bachelard’s account of discontinuity was not as radical as Kuhn’s. Bachelard was willing to speak of progress toward the truth. He made much of the fact that successor frameworks, such as non-Euclidean geometry or quantum physics, retain key predecessor results as special cases and, in effect, contextualize them.