The simple rule of rugs

All of the good [Turkish rugs] follow this rule: wherever there are two areas of color, side by side, there is a hairline of a different third color, between them. This rule is so simple to state. And yet the rugs which follow this rule have a brilliance, a dance of color. And the ones which do not follow it are somehow flat.

Of course this is not the only rule which makes a rug great—but this one rule, simple, banal, almost as it seems, will triple the brilliance and beauty of a rug. A person who knows this rule may be able to make a beautiful rug. A person who does not will almost certainly not be able to…

The depth, and spirituality, of the rug is not made less by the fact that this rule can be expressed, nor that it is so simple. What matters, simply, is that the rule is extremely deep, extremely powerful.

—Christopher Alexander, The Timeless Way of Building