'Wilderness' has a deceptive concreteness at first glance. The difficulty is that while the word is a noun it acts like an adjective. There is no specific material object that is wilderness. The term designates a quality (as the '-ness' suggests) that produces a certain mood or feeling in a given individual and, as a consequence, may be assigned by that person to a specific place.
— Wilderness and the American Mind - Roderick Nash