Under heaven all can see beauty as beauty only because there is ugliness. All can know good as good only because there is evil. Therefore having and not having arise together. Difficult and easy complement each other. Long and short contrast each other. High and low rest upon each other. Voice and sound harmonize each other. Front and back follow one another.
The tao that can be told is not the eternal Tao The name that can be named is not the eternal Name. The unnamable is the eternally real. Naming is the origin of all particular things. Free from desire, you realize the mystery. Caught in desire, you see only the manifestations. Yet mystery and manifestations arise from the same source. This source is called darkness. Darkness within darkness. The gateway to all understanding.
Clay is fashioned into vessels; it is on their empty hollowness that their use depends. Doors and windows are cut out to make a dwelling, and on the empty space within, its use depends. Thus, while the existence of things may be good, it is the non-existence in them that makes them serviceable.
Arms are instruments of ill omen.... When one is compelled to use them, it is best to do so without relish. There is no glory in victory, and to glorify it despite this is to exult in the killing of men.... When great numbers of people are killed, one should weep over them with sorrow. When victorious in war, one should observe mourning rites.
So sometimes things are ahead and sometimes they are behind; Sometimes breathing is hard, sometimes it comes easily; Sometimes there is strength and sometimes weakness; Sometimes one is up and sometimes down. Therefore the sage avoids extremes, excesses, and complacency.
The higher the sun ariseth, the less shadow doth he cast; even so the greater is the goodness, the less doth it covet praise; yet cannot avoid its rewards in honors.