Medieval Scholars Believed in the Possibility of Parallel Universes

It is strange, but for a good chunk of time religious thinkers were "more right" about subjects like the eternity of the universe than the prevailing aristotelian philosophers, sometimes deploying surprisingly modern-sounding ideas in the process. I'm thinking of authors like Philoponus https://historyofphilosophy.net/philoponus and Crescas https://historyofphilosophy.net/crescas

The Stanford Encyclopedia of Philosophy has an entry on the condemnation of 1277: https://plato.stanford.edu/entries/condemnation/

Belief based solely on faith has a pronounced tendency to go off in the weeds. That's the distinction which the scientific method makes, particularly in the tradition of the bacons -- Roger Bacon (13th c.) and Francis Bacon (16th c.), no relation. Each emphasised the value of observation or experimentation.

Second: if you find your premises, or traditional authorities, at odds with observed reality, you might care to strongly favour dismissing your premises or authorities, rather than your observations -- so long as the latter seem to be independently verifiable. An interesting case of this developed most especially in the 19th century, within the field of geology, where the record of the stones was found in marked difference to the record of the scripts, particularly the biblical record. Noted geologists spent not inconsiderable time attempting reconciliation of these records. There was no reconciliation possible, of course, one of those records was simply wrong.

https://en.m.wikipedia.org/wiki/James_Dwight_Dana#Publicatio...

Third: if you've found a persistent discord between observation and theory, then it's quite likely you've illuminated a lacuna in your knowledge or understanding. Again to geology: it was clear from the geologic record that the Earth was at least some hundreds of millions of years old, but no known force or energy could explain the observed temperature of the Earth's interior. The answer to this turned out to be previously unknown form of energy potential and release: radioactivity. That also happened to provide the clock by which the Earth's age could be determined, as well as the mechanism by which geology is ultimatley founded: plate tectonics. Not fully accepted, it turns out, until 1965, though it's now considered the fundamental organising principle of geology. Which gives us a fourth lesson:

Fourth: You can study a thing for a long, long, long time before you come to a proper understanding of it.

Fifth: Study of ancient authorities isn't wholly useless. I advise people to look to philosophy, especially, if not for truth then as a record in how the truth, and error, are arrived at, over time.

And finally: it's not enough to come to the correct answer, but to come to the correct answer through the right chain of reasoning. Science is structured knowledge. It's not a dry recitation of facts, but rather, the structure, through which, those facts become evident. If not self-evident, then building on observation and mechanism. Precursors of current understanding, absent the underlying structural foundation, are interesting, but are not science as it's properly considered.

The traditional example is that if I cross the street everything will be different. Parallel universes is related to this nonsensical multiple-parallel-futures assumption.

For those who are interesting in seeing things as they are instead of piling up nonsense upon nonsense, consider a process of evolution. There is no multiple versions of the same species because they might turn the other way. Everything happen as it happen (everything is the way it is because it got that way). It is an unfolding of a single process.

There is no future(s). It is an "organic" growth (like growing of a tree). Future is a concept of the mind. A meme. So are parallel universes. There is nothing parallel to what is. At least outside of one's head.