On The Space Where There Is Nothing

My favourite from Tao Te Ching, Chapter 11



We put thirty spokes together and call it a wheel;
but it is on the space where there is nothing that 
    the usefulness of the wheel depends.
We turn clay to make a vessel;
But it is on the space where there is nothing that
    the usefulness of the vessel depends.
We pierce doors and windows to make a house;
And it is on these spaces where there is nothing 
   that the usefulness of the house depends.
Therefore just as we take advantage of what is, we
    should recognise the usefulness of what is not.