Deconstruction
One thing it pays attention to is how opposites work. (It calls them "binary oppositions.") It says that two opposites like "good" and "bad" are not really different things. "Good" only makes sense when someone compares it to "bad," and "bad" only makes sense when someone compares it to "good." And so even when someone talks about "good," they are still talking about "bad." But this is just one thing it does.