As [Eric] Voegelin sees it, Joachim [de Fiore]’s great innovations were to conceive of history as having an eidos, a formal structure, and to “immanentize the eschaton,” to hold that the end of time will take place in time [Voegelin. The New Science of Politics: An Introduction (Chicago: University of Chicago Press, 1952), 119, 120]. Joachim held that history was not simply a series of contingent events. History consists of certain definite stages moving toward a final end. Joachim’s immanentization of the eschaton is no more paradoxical than Hegel’s end of history: time will continue, but there will be no new “ages,” the story of man will come to an end, even though men will live on. Both Joachim and Hegel hold that at a certain point all the different forms of human life and society and culture will have revealed themselves, all meaningful struggles will be over. Anything that happens afterward is simply more of the same. Both Joachim and Hegel hold that the final phase of history involves the coming into being of certain “highest” or most perfect ways of life. It is unclear, however, whether they believe that these advances have to endure, or whether certain forms out of the past may reappear, temporarily, from time to time.
Joachim’s eidos of history is the Christian Trinity.
– Hegel and the Hermetic Tradition (2001), p. 237