 Nietzsche himself suggests that the eternal recurrence was his most important thought, but that has not made it any easier for commentators to understand. Nietzsche’s articulations of the doctrine all involve hypothesizing—(or inducing the reader to imagine, or depicting a character considering)—the idea that all events in the world repeat themselves in the same sequence through an eternal series of cycles. But the texts are difficult to interpret. All Nietzsche’s official presentations of the thought in published work are either presented in hypothetical terms (GS 341), or extremely elliptical and allusive (e.g., GS 109), or highly metaphorical and quasi-hermetic (Z III, 2, 13), or all three together. Most allusions to the idea, in fact, assume that one already knows what it means—even the claims in Ecce Homo that it is the “fundamental conception” or “basic idea” of Zarathustra have this character. In the early reception, most readers took Nietzsche to be offering a cosmological hypothesis about the structure of time or of fate (see Simmel [1907] 1920; Heidegger 1961; Löwith [1935] 1997; Jaspers [1936] 1965), and various problems have been posed for the thesis, so understood (Simmel [1907] 1920: 250–1n; Soll 1973; Anderson 2005: 217 n28). Many later commentators have focused instead on the existential or practical significance of the thought (Magnus 1978; Nehamas 1980, 1985), or its “mythological” import (Hatab 2005).