Colourless green ideas sleep furiously.Yup. Colourless green ideas sleep furiously. Linguistics classes use it to demonstrate that there's more to language than just syntax (the stringing of words into sentences according to rules), that semantics is a valid intellectual discipline. The first time I heard that sentence, I blinked a few times and then laughed. It's syntactically valid -- the words are arranged according to the rules of English grammar -- but the words don't relate to one another at all, absent an extremely strange and contorted context. The mechanisms whereby we use the sounds that make up spoken language, or the glyphs that make up written language, to share mindstate with other people don't work for that sentence.
If you do try to discern what someone's thinking when they say that sentence, you reach one of a number of conclusions:
* they're telling an obscure joke, the point of which is that the sentence doesn't make any sense
* they don't understand the meanings of the words that make up the sentence
* they understand the meanings of the words, and their internal mental state is so different from yours that the sentence makes sense to them.
We call people who do the first thing a lot 'language nerds', people who do the second thing a lot 'not fluent in English', and people who do the third thing a lot 'crazy'. No, seriously. That's what crazy is. An internal mental state that deviates so far from the norm that it impairs the ability to communicate effectively. And that's why talking to crazy people makes you feel a little crazy yourself, because your mind naturally tries to make sense of what they're saying, which involves contorting your own mental state to match theirs. Hard work. Actually, getting a true 'meeting of minds' with someone, learning what they mean by what they say, is hard work even if the person isn't crazy. you have to infer a lot. Establish a shared context with them.
so...yeah. Colourless green ideas sleep furiously. Use it when someone says something that doesn't make any sense.