Holmgren's Proverb for this Principle: Don't think you are on the right track just because it's a well beaten path.
This principle highlights a vital component to Permaculture design itself... the edge. I wrote about the Importance of Edge more extensively in this post. The main thing to consider is that if there is more life and richer biodiversity in the edge, then we should do all we can to increase the edge. While the fastest route from point A to point B is a straight line, nature doesn't do straight lines. If we are truly trying to mimic nature, then we should avoid straight lines as much as possible. Of course, sometimes we need straight lines with certain design elements (roads, piping, wires, etc.), but the point is to question it when you see it. Make sure it is vital and not just for us to impart our perception of "order" on the natural world.
Valuing the Margin reminds us that the mainstream is not always right. There have been many things that have been abandoned, left on the margin, for reasons that have more to to with mass commercialism than wisdom or prudence or sustainability. I often think about the loss of all the genetic diversity and flavor in our extinct varieties of plants and animals that we call Heirloom or Heritage Food. The main reasons for their absence on our dinner plates is mainly due to shipping and storage and not flavor or consumer desire. What else on the Margin have we passed by because everyone else has ignored... ideas, tools, design, people?
"Don't think you are on the right track just because it's a well beaten path" reminds us to reevaluate what we consider not worth considering.
The interface between things is where the most interesting events take place, these are often the most valuable, diverse and productive elements in the system.
- David Holmgren