presents this concept as a hypothetical question rather than postulating it as a fact. According to Heidegger, the significant point is the burden imposed by the question of eternal recurrence, regardless of whether or not such a thing could possibly be true. The idea is similar to Nietzsche’s concept of amor fati, which he describes in Ecce Homo: "My formula for greatness in a human being is amor fati: that one wants nothing to be different, not forward, not backward, not in all eternity. Not merely to bear what is necessary, still less conceal it ... but love it." On the other hand, Nietzsche's posthumously published notebooks contain an attempt at a logical proof of eternal return, which is often adduced in support of the claim that Nietzsche believed in the theory as a real possibility. The proof is based upon the premise that the universe is infinite in duration, but contains a finite quantity of energy. This being the case, all matter in the universe must pass through a finite number of combinations, and each series of combinations must eventually repeat in the same order, thereby creating "a circular movement of absolutely identical series". However, scholars such as Neil Sinhababu and Kuong Un Teng have suggested that the reason this material remained unpublished was because Nietzsche himself was unconvinced that his argument would hold up to scrutiny. A third possibility is that Nietzsche was attempting to create a new ethical standard by which people should judge their own behaviour. In one of his unpublished notes, Nietzsche writes: "The question which thou wilt have to answer before every deed that thou doest: 'is this such a deed as I am prepared to perform an incalculable number of times?' is the best ballast." Taken in this sense, the doctrine has been compared to the categorical imperative of Immanuel Kant. Once again, however, the objection is raised that no such ethical imperative appears in any of Nietzsche's published writings, and this interpretation is therefore rejected by most modern scholars. P. D. Ouspensky Russian esotericist P. D. Ouspensky (1878–1947) believed in the literal truth of eternal recurrence. As a child, he had been prone to vivid sensations of déjà vu, and when he encountered the theory of eternal return in the writings of Nietzsche, it occurred to him that this was a possible explanation for his experiences. He subsequently explored the idea in