Arnold Zuboff published his first work on this idea in 1990, his paper "One Self", and named it "Universalism". Daniel Kolak published his book I Am You in 2004, and named it "Open Individualism". In this work he never mentions Zuboff, so perhaps wasn’t aware of him at the time. The same idea has been called by other names in the past. So how did it come about that "Open Individualism" is the name we're using now (on Reddit, Facebook, Wikipedia, Wikiquote, etc.)?
Like many people, I stumbled on the idea through my own reasoning before learning that anyone else had thought of it. When I put my first writings about it online in August of 2016, Iacopo Vettori found them and told me the idea was called "Open Individualism" and that Daniel Kolak had written a book about it. He invited me to join the Facebook group he and some others had created in 2010 under the name "Open Individualism". They also had created the Wikipedia page for Open Individualism the same year. In 2016, Iacopo was not yet aware of Zuboff, and amazingly, it seems no one else had yet dropped his name into any Facebook discussions over the course of the past six years either. I can't remember the exact year, but Iacopo told me around 2018 about discovering Zuboff's work.
I don’t think there was much discussion of the idea in academia up to this point, or at least there was no single term the idea was being discussed under. So I think Iacopo and his compatriots are the reason the term "Open Individualism" has spread rather than any other. To this day it seems to still be much more discussed in public forums like this than among academics. (In addition to the historical reason, the term “Open Individualism” does have the benefit of being distinct—"Universalism" can and does mean many different things in different contexts. But I think the primary reason it was adopted by us is historical accident.)
If anyone has any additional information to add to this, please do. For example, I don't know how this subreddit got its name.
Here's how Iacopo told me the story a few months ago:
>In regard to the preference for the term “Open Individualism”, I can say that there is only a historical reason. I found the theory by myself in 2006, and spent some time believing I was the only person in the whole world who had this idea, so I temporarily named it “the Third Hypothesis” (the first being “living a single time” and the second “living more times, but not all the lives”, as in “normal” reincarnation theories). Studying more, I found that in the Middle Ages there existed a “theist version” called Monopsychism, that Sigier of Brabant learned from Averroes, who in turn credits it to Aristotle. In this version, the soul of every man has a mortal part (I think they meant what psychologists now call “Ego”) and an immortal part, that is always the same for everybody, the “soul of God”. Then I thought that an appropriate name for the new theory could be “reductionist monopsychism” or “neomonopsychism”, where the prefix marks a substantially new (non-theistic) version compared to the traditional one.
>Only later did I learn that the book I Am You by Daniel Kolak existed, published in 2004. I read the book (and I also had an email dialog with him) so I knew that he meant the very same theory and I adopted his nomenclature. “Open Individualism” is actually an abbreviation that stands for “Open Individual View of Personal Identity”. Kolak introduced this term to contrast it with the natural view that everyone has a unique identity, called "Closed Individualism", and with the idea of Parfit and other reductionist philosophers according to which our personal identity is not stable over time, called "Empty Individualism".
>Meanwhile, I met some new friends online who were already discussing the theory and also calling it “Open Individualism”. Some of them had already emailed Kolak like me. We decided to found the Facebook group “I Am You: Discussions on Open Individualism”. The group started in 2010.
>Years later, I learned about Zuboff and his “Universalism”. I also had some email dialog with him. His presentation is quite different, but the theory is the same. The first article by Zuboff on this topic, “One Self: The Logic of Experience”, was published in 1990.
On a personal note, I prefer the term Open Individualism, because I use the Closed/Empty/Open distinction heavily in my argument for Open Individualism. But it seems everybody I know has their own preferred term for it and doesn't think Open Individualism is the best term. I started out calling it "materialist reincarnation", before I knew about OI, and then I wanted to change it to Open/Closed/Empty Existence, but then that has you calling people Open Existentialists, which is terribly confusing if you're not sitting in a Parisian café c. 1930s (and even moreso if you are), so now I just use "Open Individualism".
One other note: I've recently been studying and taking seriously for the first time both idealism and some of the south Asian philosophies like Śaiva Tantra (Christopher D. Wallis' book Tantra Illuminated, recommended by a friend with no connection to OI) that have a belief very similar to what is called idealism in Western philosophy—that mind or consciousness is the fundamental element of reality, and mind creates matter, rather than the other way around. I know many of you have been swimming in these waters for many years, and I know several people in the OI world who have spoken of Advaita Vedanta, so I am very late to the party. But reading both the Western and South Asian arguments and presentations for idealism, it seems to me that "one self" comes almost for free when you adopt idealism. (Bernardo Kastrup says as much when he comments on OI in his, um, inimitable way in the AMA video posted here four years ago.) So I'm inclined to use the term "Open Individualism" specifically for the "one self" belief attached to physicalism. There perhaps doesn't need to be an additional term for "one self" under idealism, but if you believe in physicalism, you need to have a whole separate argument to arrive at it. (I would say "whole separate very elaborate argument", lol.)