Permaculture has a value-added factor that extends beyond what might be merely maintained or sustained, which is the quality of 'regeneration'. All sustainable solutions are unsustainable over the longer term, if they are not also intrinsically regenerative. The word “regenerative” means “the capacity to bring into existence again”; hence, if an item or system is regenerative, it has the inherent capacity to bring itself into existence once more. To achieve this for a completely artificial system is a challenge. Nature offers the ultimate example of a design that is both sustainable and regenerative, and it is logical to appeal to natural principles for solutions to many of our current problems. Within a broader perspective of regenerative design, permaculture identifies the elements of sustainable living which are harmonious with nature.