¿Qué significa 1. What does "metal funiture" mean in this context?
2. Is it grammatically correct to say this sentence"…so blocks our view that…"? Shouldn't it be "so blocking our view that"?
3. Does the word "persons" somewhat the same as "individuals"? ?

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1. “Mental furniture” is used, I think, because the author had already used “blinders” to established the metaphor of a room. So in this context, it may mean something about the model that impedes the person trying to use it (like furniture stops someone from moving around a room).
2. No, the author is correct here. “So” in this context is used as a synonym for “in such a way”. So if you imagine that he’s saying “blocks the view in such a way that”, it makes more sense.
3. Literally, “our persons” here actually means something like “our bodies” or “ourselves”.