Lao Tzŭ's teaching is contained in a small book, the _Tao Tê Ching_, the "Book of the World Law and its Power". The book is written in quite simple language, at times in rhyme, but the sense is so vague that countless versions, differing radically from each other, can be based on it, and just as many translations are possible, all philologically defensible. This vagueness is deliberate. Lao Tzŭ's teaching is essentially an effort to bring man's life on earth into harmony with the life and law of the universe (Tao). This was also Confucius's purpose. But while Confucius set out to attain that purpose in a sort of primitive scientific way, by laying down a number of rules of human conduct, Lao Tzŭ tries to attain his ideal by an intuitive, emotional method. Lao Tzŭ is always described as a mystic, but perhaps this is not entirely appropriate; it must be borne in mind that in his time the Chinese language, spoken and written, still had great difficulties in the expression of ideas. In reading Lao Tzŭ's book we feel that he is trying to express something for which the language of his day was inadequate; and what he wanted to express belonged to the emotional, not the intellectual, side of the human character, so that any perfectly clear expression of it in words was entirely impossible. It must be borne in mind that the Chinese language lacks definite word categories like substantive, adjective, adverb, or verb; any word can be used now in one category and now in another, with a few exceptions; thus the understanding of a combination like "white horse" formed a difficult logical problem for the thinker of the fourth century B.C.: did it mean "white" plus "horse"? Or was "white horse" no longer a horse at all but something quite different? Confucius's way of bringing human life into harmony with the life of the universe was to be a process of assimilating Man as a social being, Man in his social environment, to Nature, and of so maintaining his activity within the bounds of the community. Lao Tzŭ pursues another path, the path for those who feel disappointed with life in the community. A Taoist, as a follower of Lao Tzŭ is called, withdraws from all social life, and carries out none of the rites and ceremonies which a man of the upper class should observe throughout the day. He lives in self-imposed seclusion, in an elaborate primitivity which is often described in moving terms that are almost convincing of actual "primitivity". Far from the city, surrounded by Nature, the Taoist lives his own life, together with a few friends and his servants, entirely according to his nature. His own nature, like everything else, represents for him a part of the Tao, and the task of the individual consists in the most complete adherence to the Tao that is conceivable, as far as possible performing no act that runs counter to the Tao. This is the main element of Lao Tzŭ's doctrine, the doctrine of _wu-wei_, "passive achievement".