Concepts are defined by their opposites. For example, you can't have white without black, nor sound without silence. If there was only white, you wouldn't see it as white, because you need the existence of black to compare and contrast it with. The same is true of all opposing concepts. So when you ring a bell for example, you are not only producing sound, but also the silence. And when the bell is silent, it is also ringing. Remember, we are talking about concepts here. When the bell rings, the concept of silence is produced along with the concept of sound, and vice versa. If it didn't, we wouldn't be able to recognise the sound as sound. The implication of this is alluded to within the design of the Chinese yin/yang symbol. Notice that there is a black spot inside the white area, and a white spot inside the black area, and the black and white areas are moving into each other via the S shape. When you bring opposing concepts together, they cancel each other out, leaving simply 'that which is'. In other words, what you're left with is reality free from concepts. Incidentally, the symbol for Zen Buddhism is a simple circle. It represents the circle which surrounds the yin/yang symbol. The black and white areas inside the circle have been combined and have cancelled each other out, leaving the circle empty, emptiness being the word used to decribe the absense of the 'self' concept in Buddhism, not only as an imagined concept pertaining to ourselves, but also as the concepts and labels which we superimpose upon the world around us in order to facilitate our interaction with it. The realisation that opposing concepts cancel each other out is yet another way by which we can realise the fallacy of separation between objects in the world, and by extension the fallacy of separation of ourselves with the world, since our bodies are also objects to which concepts are applied.
"The foolish reject what they see, not what they think. The wise reject what they think, not what they see." - Huang Po.