The sound of one hand clapping...

http://www.firstain.com/index.php/2011/02/14/valentines-special-us-engineer-invents-special-bra-that-unhooks-automatically-when-you-clap/

Zen Koan; a philosophical riddle; brought the interesting view on the meaning of "the sound of one hand clapping". He states that it is the same as two hands clapping. Two hands clapping together make a sound. We can also notice that one hand clapping (the movement of the fingers onto the palm of the hand) makes the same sound (or a similar one).
His theory highlights the fact that two hands are in a relationship when clapping together.One hand can clap; it means that we don't need for  both sides of the relationships to act to bring change. (clapping)
It can also relate to relationship in general. If one person makes the first move; it will be beneficial for both parties.One party can bring change. When one side of the relationship changes; the other has to do the same to keep up. We can conclude that we don't have to wait for others to make the first move; as it will benefit both parties in the relationship.

Source: http://www.huna.org/html/onehand.html