One Past But Many Futures

Two Histories of England both include the Norman Conquest but might explain and interpret the Conquest very differently. Of two future histories, by Olaf Stapledon and HG Wells respectively, the first includes Martian invasions of Earth whereas the second does not. Both Wells and Poul Anderson have their versions of a Martian invasion of Earth but not as part of their future histories. Thus, the future is even more diverse than the past. Indeed, we speak of "futures" and even of "Futures" as an academic discipline. Futurologists consult historians, economists, sf writers etc.

However, the past has the advantage of reality. There is always more that the chronicles have not told us. Even if Poul Anderson had devoted his entire career to writing different kinds of narratives set inside a single future history, he could not possibly have matched the sheer number of histories and biographies set on Earth Real. Millions of real people really did live and die in World War II. We can only imagine that even larger numbers lived and died during the Chaos, the Troubles and the Long Night. But we must imagine this if we are to appreciate Anderson's Technic History properly.