There are many people who have either directly or indirectly helped me with the completion of this book. The foremost of them is Professor Sir Karl Popper. I started corresponding with him in 1989 when he was already eighty-eight years old. Wanting to understand Lao Tzu in depth, I had inadvertently developed the urge to re-read his Open Society and Its Enemies. I felt that there were many agreements between Lao Tzu and Popper, yet Popper has successfully analyzed these tenets in more convincing modern terms. Later, wanting to understand him more precisely, I further extended my reading to his other book The Logic of Scientific Discovery,(orig. Logik der Forschung) which has laid the foundation for Open Society. Through it I realized why and how his claims are so solidly grounded. I have also gained from it some insight of the methodology of his analysis. Popper's own translation of Plato's original work in Open Society, according to Bertrand Russell "A work of first-class importance attack on Plato, while unorthodox, is in my opinion, totally justified." Other British Platonic scholars, including adversaries, also can not find fault in his translation. Popper's other monumental book Conjectures and Refutations: The Growth of Scientific Knowledge especially expounds the tenet that our knowledge is not immutable. In the book he successfully proves that either more evidences or new thinking mode will impel us to eke out new and better theories about us and cosmos. Popper has also laid out guidelines how to determine the superior acceptability of one theory over another.

Nevertheless, since 1950's Popper was working hard on the Postscript in order to perfect, as well as to simplify, his axioms in "The Logic of Scientific Discovery". This project, as his editor W.W.Bartley, III, describes "represents the culmination of Sir Karl's work in the philosophy of physics", particularly in quantum theory. Bartley finally edited and published Popper's "Postscript" in 1982. They appeared as three books titled Realism And The Aim of science, The Open Universe: An Argument for Indeterminism, and Quantum Theory And The Schism in Science. These books are far more difficult to read than all his other books, particularly if a person is not knowledgeable of mathematics and modern physics, Popper agreed with me sympathetically.

I visited Popper on March 14 of 1994 when he was almost ninety-two years old. I was so impressed then by the sharpness and speed of his mind, his persistence, his amazing memory(of even contents of our correspondence), his poet-like compassion, and his unparalleled self-sacrificing devotion to the quest of truth. As a person he was so unpretentious and unaffected by social honors. He invited me back to visit him with my husband the following year, and promised by then he should have finished his four books he was working on. After that he would have time to write a Preface for my yet-to-come book on Lao Tzu. He seemed have something to say about Lao Tzu's philosophy, which he had tried to figure out since his early youth. In spite of Popper's age, his consistent support and encouragement until his death in l994 has given me a great boost, which was responsible for my eventual breakthrough few months before I visited him. The greatest sorrow is that I can not present my book to him now. The old work I have presented to him was even printed with the obsolete dot-matrix printer, matched by the awful crudity of its content.

If my English is acceptable, I owe it to Professor Sir Alfred Ayer, a great writer of philosophical essays. He was responsible for my staying with philosophy by bringing me to Oxford University to do graduate work. However, his recommendation was "she was very bright and naive". I went there with the hope to deepen my knowledge of the philosophy of Bertrand Russell, Ayer's mentor and good friend. Unfortunately, due to then circumstance there, Russell was considered outmoded, and Ayer was never allowed to be my supervisor. I could have been exceedingly benefited by his heuristic teaching and non-dogmatic approach to philosophy. Besides, like Popper, he also held Russell with high esteem. This, however, has never dampened my enthusiasm about Rusell, who may be the most formidable contender for the honor of the greatest philosopher of the twentieth century. I always admire Ayer's talent of expressing very deep and fine philosophical thought in plain simple English with lucidity and elegance. His book Language, Truth And Logic had persuaded me that philosophy was still a viable study, immune to Ralph Waldo Emerson's criticism in "The American Scholars". Ayer and I have continued our correspondence for a total of twenty-nine years until his death in 1989. However, he once told me while I was in Oxford that he thought that I could be a better poet than a philosopher. But I have never written any poem, in either Chinese or English. When I first attempted to translate Lao Tzu back in 1985, he gave me a double-edged criticism of my translation. He said that my English was "laboured"(pompous). As a rule such practice had obscured the articulation of my comprehension of Lao Tzu's deep thoughts. In any case, he said later that I should make a serious effort to complete the whole project, and say it spontaneously with what I have understood. To be fair to Sir Alfred(Freddie) the version he had read was the result of my preliminary attempt on this task, whereas the one(1999 translation) adopted in this book was the result of my twelfth or so tryout afterward. As a philosopher, Ayer was modest in expressing his deep thoughts.

My special thanks to Professor Chern, Shiing-Shen of the Unversity of California, Berkeley for his agreement to do the calligraphy of the Chinese title. I had read news about Professor Chern's doing pioneering work in mathematics (topology and geometry) even while I was in high school. He is responsible for the introduction of both Chern's Characteristic Class and Chern-Weil Theory. Back in 1960 he was elected member of The National Academy of Sciences. He was also the founder of The National Mathematical Science Research Institute(MSRI), which is also situated in Berkeley. Professor Chern was brought up in Chiashing of Chiangshu province, the area was a well-known as the hotbed of many poets and men of letters. His early education was evidently traditional, even his demeanor is Confucian. He started writing traditionally classical Chinese poems since he was in his early teens, and it continues until this day. Between 1911 and 1937 Chinese went through a great deal, politically, socially, and culturally. Extraordinarily abundant creative and innovative thoughts also mushroomed then. When he studied in Beijing in 1920-30's, then heated controversy over whether Confucius lived before Lao Tzu attracted his attention. For years he did not have a chance to articulate his thoughts about it. Back in 1996, I presented to him both my Chinese and English translations of Lao Tzu. Hopefully, I have successfully proved and reinforced his insight that it is silly to challenge the venerated historical report that Lao Tzu lived between the sixth and seventh centuries BCE.