In the course of the past several chapters, we have discussed the basic mechanisms responsible for a variety of phenomena that occur in nature. But in trying to explain our actual experience of the natural world, we need to consider not only how phenomena are produced in nature, but also how we perceive and analyze these phenomena. For inevitably our experience of the natural world is based in the end not directly on behavior that occurs in nature, but rather on the results of our perception and analysis of this behavior.