The small book that he wrote, the Dao De Jing or Lao Zi, is written verse, it is said to contain great wisdom. It has been studied by Chinese scholars of all ages after him, and many notes and commentaries have been written to attempt to explain the meaning of every line in the book. It goes over many different philosophical and practical questions, such as the origin and working of the universe, the correct way to live and behave, the laws that govern the change, and movement of things, and the way to govern a state. This book is split up into two main sections, the Dao and the De. Out of the total 81 chapters the Dao part is 37 chapters long while the De contains 44 chapters.
Dao translated means the way or path. It is the source of all; it is the eternal, invisible, and indescribable energy that gave birth to the universe. In other words it is the way everything in the universe is. This shows that Lao Zi, did not believe that the universe was created by a God. Instead it was created by a mysterious force which he called Dao, but he said that the name itself was inadequate. De translated means virtue or power. It is the power of something to be whatever it is and to do whatever it does. For example, the De of a cup lets you hold liquid without it spilling on yourself and staining your clothes. Or De can also be seen as the virtue of something that makes it uniquely whatever it is and to do whatever it does. This means that the De of an uncarved block of wood is not to just be a block of wood, but it is its inherent ability to be shaped or formed into anything, maybe even a cup.
Lao Zi held that all things and concepts are relative. The long and the short, the high and the low, what is in front and what is behind, what is beautiful and what is ugly, must exist in pairs. In each pair one side produces the other. The two sides are opposite to but dependent on each other. It is from this that he drew his conclusion: "turning back is how the Way (Dao) moves". In other words, things always go from one extreme to the other. What is strong may become weak, and what is weak may become strong. It is not difficult for one to name facts that show this theory is true. There have been innumerable stories of the collapse of conquerors. Lao Zi praised weakness and softness, which, he said, will eventually overcome the strong and hard.
Another concept that Lao Zi stresses over and over again in the Dao De Jing, is Wu Wei. Wu Wei means action non-action. This is when someone does something, and it is an authentic part of that person. As to feel, to seem, and indeed to really be effortless. It must come from deep within. It is what is second hand and not the result of a decision or effort. There is no because, it is just done. An example that Lao Zi gives is plain old water. It sustains all life, it erodes the hardest substances, and water does this all by patiently, effortlessly being itself. It is when doing absolutely nothing, everything is done. It is the De of the Dao that, by Wu Wei, all is accomplished.