Today's post, Reductionism was originally published on 16 March 2008. A summary (taken from the LW wiki):
We build models of the universe that have many different levels of description. But so far as anyone has been able to determine, the universe itself has only the single level of fundamental physics - reality doesn't explicitly compute protons, only quarks.
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It seems to me that the reductionism as advocated by Eliezer is a poor-quality model. It only works one way: you can potentially trace the 747 all the way down to its subatomic particles, but you cannot construct a particular configuration of subatomic particles that will fly, rather than bark or crawl, using just the laws of QFT. Thus it has no testable predictions (that everything we can see or touch consists of quarks, leptons and gauge bosons is not a prediction, but an observation), just like his other favorite myth, the MWI. He dislikes the term "emergence", and he is entitled to his emotions, but the sad experience is that nuclear physics is no help in psychology, not even after you say "reductionism" three times.
Saying "you cannot" is awfully gutsy. Are you familiar with renormalization groups? They're a mathematical tool for getting high-level laws out of low-level laws. The only theoretically unsolved problem I know of between QFT and predicting planes is the prediction of a periodic solid as the ground state of your structural metal, though there are probably a few more.