Et tu, Brute
Here's an 8-part lecture on the philosophy of mind, given by John Searle. I've only seen the first bit (I'll watch the rest if I get the time), but it seems like a nice introduction to the field.
He gets into what he has earlier called the "brute fact vs. social fact" distinction at the end of part 1. This brought up something I was reading about that distinction last year around this time, as I was finishing up my MA thesis. This is how I remember it:
The brute facts are the world, independent of the observer. The social facts are facts that depend on social decisions and, I guess, aesthetics: matters of taste, in the broadest possible sense (what to do: commit mass murder or have a nice cup of tea?).
You kick a rock, Newton says, the rock will brutalise your foot. The rock and its physical nature is a brute fact which bruises your foot. The physical pain is a brute fact too, probably - neural signals and responses. But what the pain means is a social fact. It depends on you and your community's relationship to physical pain and/or rocks.
In general, as a rule, I think we can almost never go wrong if we assume that most facts are social facts. Even things which seem very obviously to be brute facts, like said rock, are, when you think about it, crawling with social facts: what do you think about rocks? What do you think about pain? Why do you kick the rock? Have you kicked rocks before? Does the rock remind you of your mother? Etc. Etc.
Michael Bérubé has an argument which I think I agree with in his book Rhetorical Occasions that the distinction between what is a brute fact and social fact is a social fact, in the day-to-day business of being alive. If you believe the rock is an illusion, the rock doesn't stop being a brute fact, and if you change your mind upon having kicked it, it doesn't care. But in the interaction with your community, there is no solid basis to ever completely arbitrate the dispute over what is a brute fact and what is a social fact. You can change your community's mind, but their state of mind is generally much further from the brute facts than one would think.
I mean, kicking the rock is a pretty damn convincing argument, but it's still rhetoric.