"A complex system that works is invariably found to have evolved from a simple system that worked..."

I thought this quote, quoted on the 37 signals blog was so quotable it was worth quoting here:

A complex system that works is invariably found to have evolved from a simple system that worked. A complex system designed from scratch never works and cannot be patched up to make it work. You have to start over, beginning with a working simple system. - John Gall