Notes for the [QP Sequence](https://www.lesswrong.com/posts/hc9Eg6erp6hk9bWhn/the-quantum-physics-sequence) book club on twitter group chat. # Week 0 ## Preliminaries ### [Probability is in the Mind](https://www.lesswrong.com/lw/oj/probability_is_in_the_mind/) ^prob-is-the-mind This post is sorta a rehash of [Map and Territory](https://www.lesswrong.com/tag/map-and-territory-sequence). It's in reference to the holy war of Bayesians vs Frequentists, which is related to quantum because Eliezer's hero [E. T. Jaynes](https://bayes.wustl.edu/) wrote a lot of stuff about both Bayes & quantum and drew a bunch of connections. The tl;dr is that a "probability" is a subjective degree of belief, not a fact about the world. A coin doesn't have an "inherent 50% probability" - in fact the coin is fully deterministic with regular Newtonian physics! The "50%" represents your knowledge of the coin. In quantum stuff, this will come up because there is a thing called a "probability amplitude" and people get confused about whether these amplitudes and probabilities "actually exist" or whether they are just tools for predicting stuff. The answer isn't super straightforward either way, but it's good to be aware that (at least classically) plain "probabilities" like in coins aren't out there in the territory, so you aren't tempted to use that as an analogy for quantum stuff. If you want to read a whole book about this (which this post is mostly based on), it's [Probability Theory](https://www.amazon.com/Probability-Theory-Science-T-Jaynes/dp/0521592712) by Jaynes. ### [Reductionism](https://www.lesswrong.com/posts/tPqQdLCuxanjhoaNs/reductionism) ^reductionism Reductionism is the idea that _in theory_ if you could describe everything in terms of the lowest-level fundamental physics, that would be all you need to know. Sure, we can't actually do that _in practice_, and that's acknowledged in the post, but that's a statement about our maps ("this map isn't efficient enough to compute", etc), not the territory. The territory itself is made out of the lowest level. This will matter for quantum stuff because if you accept that tiny particles follow rules of quantum mechanics, then that means tables and chairs and people (which are made of those particles) are also going to have to follow those rules. ### [Joy in the Merely Real](https://www.lesswrong.com/posts/x4dG4GhpZH2hgz59x/joy-in-the-merely-real) ^joy-in-real Sometimes it's fun to believe in magic. But the world isn't actually made out of magic, so that might suck if your idea of fun is only allowed if it's magical & mysterious. So this post is pointing out that there's a type of fun when you're discovering how things actually work. That way you don't have to be really sad while you are learning physics. ### Zombies ^zombies Two posts about zombies are included in the preliminaries. #### [Zombies! Zombies?](https://www.lesswrong.com/lw/p7/zombies_zombies/) ^zombies-1 > FYI there is a ~25% shorter rewritten version of this post at [Zombies Redacted](https://www.lesswrong.com/posts/7DmA3yWwa6AT5jFXt/zombies-redacted). What is consciousness? By consciousness, we mean that there is something-that-it-is-like to be you, as in Nagel's [What Is It Like to Be a Bat?](https://en.wikipedia.org/wiki/What_Is_It_Like_to_Be_a_Bat%3F). One way to talk about the "hard problem of consciousness" is to talk about zombies. Philosophical zombies that is - an atom-for-atom identical copy of a person, with the only difference that they have _no_ subjective experience. Is it possible for such a zombie to exist? Probably not, most agree, even the people who talk about zombies exist. But would it be imaginable or conceivable in some other universe? If so, then our universe has a special different property than that universe - the extra property of having subjective experiences. Anyway this is a long post and and a long argument that's hard to summarize. The argument in the post is that zombies are not a coherent idea, because consciousness actually does affect the physical world (e.g. by making people write blog posts about consciousness) and so you can't just make a copy and remove the consciousness and have it do the exact same stuff. #### [The Generalized Anti-Zombie Principle](https://www.lesswrong.com/posts/kYAuNJX2ecH2uFqZ9/the-generalized-anti-zombie-principle) ^zombies-2 This post argues that the same principle that precludes zombies also applies to things like teleporters or mind-uploading. That is, believing that an upload isn't "really you" is equivalent to believing in zombies, according to the post. This one is a shorter post and I don't think it clearly spells out why - just makes the claim and asks you to think about it. ### [Belief in the Implied Invisible](https://www.lesswrong.com/posts/3XMwPNMSbaPm2suGz/belief-in-the-implied-invisible) ^implied-invisible The universe still exists past the edge of your telescope. This is different from the previous zombie posts, which are about the "additional invisible" instead. The difference between "implied invisible" and "additional invisible" is that implied is good to believe in and additional is bad to believe in. This will be extremely relevant for quantum, because of the huge number of implied invisible branches in many worlds.