In '63…'64 I worked on trying to understand quantum mechanics, and I brought in Felix Villars and for a while some comments... there were some comments by Dick Feynman who was nearby. And we all agreed on a rough understanding of quantum mechanics and the second law of thermodynamics and so on and so on, that was not really very different from what I'd been working on in the last ten or fifteen years. I was not aware, and I don't think Felix was aware either, of the work of Everett when he was a graduate student at Princeton and worked on this, what some people have called 'many worlds' idea, suggested more or less by Wheeler. Apparently Everett was, as we learned at the Massagon [sic] meeting, Everett was an interesting person. He… it wasn't that he was passionately interested in quantum mechanics; he just liked to solve problems, and trying to improve the understanding of quantum mechanics was just one problem that he happened to look at. He spent most of the rest of his life working for the Weapon System Evaluation Group in Washington, WSEG, on military problems. Apparently he didn't care much as long as he could solve some interesting problems! Anyway, I didn't know about Everett's work so we discovered our interpretation independent of Everett. Now maybe Feynman knew about… about Everett's work and when he was commenting maybe he was drawing upon his knowledge of Everett, I have no idea, but… but certainly Felix and I didn't know about it, so we recreated something related to it. Now, as interpreted by some people, Everett's work has two peculiar features: one is that this talk about many worlds and equally… many worlds equally real, which has confused a lot of people, including some very scholarly students of quantum mechanics. What does it mean, 'equally real'? It doesn't really have any useful meaning. What the people mean is that there are many histories of the… many alternative histories of the universe, many alternative course-grained, decoherent histories of the universe, and the theory treats them all on an equal footing, except for their probabilities. Now if that's what you mean by equally real, okay, but that's all it means; that the theory treats them on an equal footing apart from their probabilities. Which one actually happens in our experience, is a different matter and it's determined only probabilistically. Anyway, there's considerable continuity between the thoughts of '63-'64 and the thoughts that, and… and maybe earlier in the ‘60s, and the thoughts that Jim Hartle and I have had more recently, starting around '84-'85.
