"At the core of dualism, according to Zen, are words--just plain words. The use of words is inherently dualistic, since each word represents, quite obviously, a conceptual category. Therefore, a major part of Zen is the fight against reliance on words. To combat the use of words, one of the best devices is the koan, where words are so deeply abused that one's mind is practically left reeling, if one takes the koans seriously. Therefore it is perhaps wrong to say that the enemy is logic; rather, it is dualistic, verbal thinking. In fact, it is even more basic than that: it is perception. As soon as you perceive an object, you draw a line between it and the rest of the world; you divide the world, artificially, into parts, and you thereby miss the Way. "
~Douglas Hofstadter; Godel, Escher & Bach~