Once again, I came across the notion (in a lay physics book by an academic) that two mutually exclusive states simultaneously exist until observed (based on the Schrödinger living/dead cat thought experiment), which, on its face, seems to me to belong to theology and not to science. That both mutually exclusive states are simultaneously possible is logical; but that both mutually exclusive states are being simultaneously fulfilled is not. Whether states are observed and whether an observer exists are irrelevant to the state of the states. I understand that the claim extends from two to three and to infinitely many states; I see that as just as illogical. (The latest source where I read of this is Neutrino Hunters: The Thrilling Chase For a Ghostly Particle to Unlock the Secrets of the Universe, by Ray Jayawardhana (author physics prof., York Univ.) (N.Y.: Scientific American / Farrar, Straus and Giroux, 1st ed. [1st printing?] hardback (ISBN 978-0-374-22063-1) 2013); the relevant passage is at p. 29 ("The determinism of classical mechanics gave way to mere statistical probabilities: instead of predicting definitive outcomes, quantum mechanics assigns likelihood to different results. That meant, as Erwin Schrödinger pointed out in a famous thought experiment, a cat in a box could be both alive and dead at the same time, until an observer intervenes by looking in."). I agree with the first quoted sentence but not the second in that we can grant that the probability of the first sentence has not been resolved but it does not follow that the two states are simultaneously fulfilled. To me, that's a non sequitur. It doesn't say, "could be either alive or dead"; it says, "both alive and dead at the same time".) I've seen similar statements several (maybe many) times in different science sources. But I gather my disagreement means that I don't know physics. Is there a reliable lay publication that sets out a proof for simultaneous preobservational existence of that which is mutually exclusive? I poked around this forum, which listed five topics as similar. <https://www.physicsforums.com/threads/schroedingers-cat-explanation.682271/#post-4329868> says many experiments prove this. I'd like to read about those, for example. I am not asking that someone explain the whole thing on this forum. I'm happy to read a book or an article or two or three by authors who are in one of these professions (not simply a professional writer, but a physicist or related academic). Do you know any you could recommend?