looks like i linked the wrong post, meant to link the previous one ( http://lesswrong.com/lw/eva/the_fabric_of_real_things/ ). Quote anywya:

For a statement to be comparable to your universe, so that it can be true or alternatively false, it must talk about stuff you can find in relation to yourself by tracing out causal links.

yea, not a very good one, I'm really tired and can't find a better one at the moment, I remember there were some in there somewhere...

Rationalist taboo is supposed to get around the problems associated with fuzzy human words. There might still be problems with more direct forms of reference in theory, but in practice the word specific ones are usually enough.

"Not" is one of those things that reduce to math. Specifically, the formal system of boolean algebra.