A standard traditional Chinese book on dream-interpretation is the Lofty Principles of Dream Interpretation (夢占逸旨) compiled in the 16th century by Chen Shiyuan (particularly the "Inner Chapters" of that opus).[12][13][14][15] Chinese thinkers also raised profound ideas about dream interpretation, such as the question of how we know we are dreaming and how we know we are awake. It is written in the Chuang-tzu: "Once Chuang Chou dreamed that he was a butterfly. He fluttered about happily, quite pleased with the state that he was in, and knew nothing about Chuang Chou. Presently he awoke and found that he was very much Chuang Chou again. Now, did Chou dream that he was a butterfly or was the butterfly now dreaming that he was Chou?" This raises the question of reality monitoring in dreams, a topic of intense interest in modern cognitive neuroscience