Because in our culture we overvalue the intellect, we imagine that to become enlightened demands extraordinary intelligence. In fact, many kinds of cleverness are just further obscurations. There is a Tibetan saying: "If you are too clever, you could miss the point entirely."
Patrul Rinpoche said: "The logical mind seems interesting, but it is the seed of delusion." People can become obsessed with their own theories and miss the point of everything. In Tibet we say: "Theories are like patches on a coat, one day they just wear off."-Sogyal Rinpoche