What worries me is the apparent refusal to engage with the rational critics of reductionism. But I am mainly thinking of critics in fields other than physics - politics "there is no such thing as society", Skinner's psychology, "there are no thoughts, only stimuli and responses", not to mention developmental biology, weather forecasting & even mechanical engineering analysis, none of which actually get near "the territory" of quarks and leptons. So I am beginning to suspect that reductionism is used in a special sense by EY, more or less as a synonym for monism. And it's true, I wouldn't want to defend "substance dualists".

What you are calling reductionism here is the refusal to countenance some higher-level properties. But, in fact, most reductionists do countenance most h-l properties. What makes them reductionists (which of course is not brought out by the broken LW wiki definition) is that they think all the h-l properties they countenance can be explained at a lower level. BTW, people who don't countenance any h-l properties, states, or entities are called mereological nihiists, not reductionists.

As for the Naval Gunner, the point is that he would be right in other fields than fundamental physics. In weather forecasting long term forecasts using coarser models are actually more accurate than those using fine meshes, because of the chaotic behaviour at smaller scales.

I don't quite agree here. It's true that chaotic interactions and floating point multiplication errors mean that long-running fine-grained maps are less accurate than long-running coarse-grained maps, but it seems cleaner to consider that a fact about computer science, not meteorology.

Thanks for pointing to the more recent EY post, which I look forward to reading. No time tonight.

I would actually recommend Hands vs. Fingers first if you haven't read it yet. It's shorter and may be more directly relevant to your interests.