Welcome to the Rationality reading group. This fortnight we discuss Part R: Physicalism 201 (pp. 983-1078). This post summarizes each article of the sequence, linking to the original LessWrong post where available.
R. Physicalism 201
214. Hand vs. Fingers - When you pick up a cup of water, is it your hand that picks it up, or is it your fingers, thumb, and palm working together? Just because something can be reduced to smaller parts doesn't mean that the original thing doesn't exist.
215. Angry Atoms - It is very hard, without the benefit of hindsight, to understand just how it is that these little bouncing billiard balls called atoms, could ever combine in such a way as to make something angry. If you try to imagine this problem without understanding the idea of neurons, information processing, computing, etc you realize just how challenging reductionism actually is.
216. Heat vs. Motion - For a very long time, people had a detailed understanding of kinetics, and they had a detailed understanding of heat. They understood concepts such as momentum and elastic rebounds, as well as concepts such as temperature and pressure. It took an extraordinary amount of work in order to understand things deeply enough to make us realize that heat and motion were really the same thing.
217. Brain Breakthrough! It's Made of Neurons! - Eliezer's contribution to Amazing Breakthrough Day.
218. When Anthropomorphism Became Stupid - Anthropomorphism didn't become obviously wrong until we realized that the tangled neurons inside the brain were performing complex information processing, and that this complexity arose as a result of evolution.
219. A Priori - The facts that philosophers call "a priori" arrived in your brain by a physical process. Thoughts are existent in the universe; they are identical to the operation of brains. The "a priori" belief generator in your brain works for a reason.
220. Reductive Reference - Virtually every belief you have is not about elementary particle fields, which are (as far as we know) the actual reality. This doesn't mean that those beliefs aren't true. "Snow is white" does not mention quarks anywhere, and yet snow nevertheless is white. It's a computational shortcut, but it's still true.
221. Zombies! Zombies? - Don't try to put your consciousness or your personal identity outside physics. Whatever makes you say "I think therefore I am", causes your lips to move; it is within the chains of cause and effect that produce our observed universe.
222. Zombie Responses - A few more points on Zombies.
223. The Generalized Anti-Zombie Principle - The argument against zombies can be extended into a more general anti-zombie principle. But, figuring out what that more general principle is, is more difficult than it may seem.
224. GAZP vs. GLUT - Fleshes out the generalized anti-zombie principle a bit more, and describes the game "follow-the-improbability".
225. Belief in the Implied Invisible - That it's impossible even in principle to observe something sometimes isn't enough to conclude that it doesn't exist.
226. Zombies: the Movie - A satirical script for a zombie movie, but not about the lurching and drooling kind. The philosophical kind.
227. Excluding the Supernatural - Don't rule out supernatural explanations because they're supernatural. Test them the way you would test any other hypothesis. And probably, you will find out that they aren't true.
228. Psychic Powers - Some of the previous post was incorrect. Psychic powers, if indeed they were ever discovered, would actually be strong evidence in favor of non-reductionism.
This has been a collection of notes on the assigned sequence for this fortnight. The most important part of the reading group though is discussion, which is in the comments section. Please remember that this group contains a variety of levels of expertise: if a line of discussion seems too basic or too incomprehensible, look around for one that suits you better!
The next reading will cover Part S: Quantum Physics and Many Worlds (pp. 1081-1183). The discussion will go live on Wednesday, 27 January 2016, right here on the discussion forum of LessWrong.