Perhaps the greatest yin-yang is duality and non-duality. David Loy, in his book Nonduality presents the following translation of the Tao Te Ching Chapter 1:
The Tao that can be Tao'd is not the constant Tao
The name that can be named is not the constant name
Having-no-name is the source of heaven and earth
Having-names is the mother of the ten thousand things
Therefore, always have no intention in order to see the wonder
Always have intention in order to see the forms
These two things have the same origin
Although different in name
Their sameness is called the mystery
From mystery to mystery: the gate of all wonder!
According to David Loy, this alternates the dual and non-dual view. There is the nameless source, and the diverse named things. There is a state beyond labeling and intention, and there is a state full of things. Together, they make up the one Tao.
To connect this to personal experience, imagine sitting in meditation listening to a dog bark. There will be a bare sensation of the barking, generally followed by thoughts and feelings. There may appear in the mind an image of a dog, memories of dogs, emotional impulses of irritation or fear. Thinking "there is a dog barking and it is annoying me" is from the point of view of the ten thousand things. Having a field of awareness in which things arise and pass is from the point of view of unity, of non-dualism.
One important thing that this points out is that there is nowhere to go. The non-dual state is not something else. It is not full of light and bliss and angels singing sweet songs of divine delight. It is not on a different dimension or plane of existence. The ten thousand things and the nameless source are the same.
The difference between the two is the overlay of thoughts, feelings, perceptions, associations: the naming and labeling we generally impose on experience. In Buddhism, we would start with rupa, form. Form doesn't mean anything. It's not good or bad. It just is what it is. There is a sound of the dog bark, the sight of the moon shining, the feel of the wind blowing. To this would be added vedana, or feeling. I like the wind, but I don't like the dog. Then comes perception. There's that dog bark, that moon. Then come the reactions: the dog barking colors my mood, my thoughts turn to how I hate the dog barking, how I wish it would stop, to ceaseless talking about the dog. Then comes vijnana, discriminating consciousness.
This shows the progression in Buddhist terms from the nameless to the named.
With the Tao, we don't try to elevate one or the other. It does not say we should always remain without intention, without the mental and emotional overlay we place on things. It says to see the wonder, be without intention. To see the forms, be with intention. In true non-clinging fashion, we can move between both worlds.
As the Tao Te Ching says later:
Without going out the door, know the world
Without peering out the window, see the Heavenly Tao
The further one goes
The less one knows
Therefore the sage
Knows without going
Names without seeing
Achieves without striving