Book excerpt: In summary, we may declare that Lao-tzu is an authentic philosopher and he uses a clear logic to describe his principle in the Tao Te Ching. Tao philosophy deals with the nature of reality. We come to such a conclusion despite the overwhelming belief to the contrary. We no longer need to accept Tao philosophy as a mysterious philosophy. Instead, we have shown that there is a definite principle and a clear logic in the Tao Te Ching. The principle and logic can be shown with a systematic model based on the words of Lao-tzu. The results are well beyond what we could have expected when we started this project more than a decade ago. This work represents a major step in our understanding of Tao philosophy. This book shows the complete logical structure of Tao philosophy, which can serve as the ultimate base for a consistent interpretation of the Tao Te Ching. The logic of Tao philosophy is precise and can be presented analytically.