Imagine that we decide to take a relaxed walk in the woods. In a beautiful glade we pause and look around us. Suppose that the first thing we notice is how green everything is. There are all these little leaves and they are all green. Of course, if we look a little closer, we find that, although all the leaves are green, there still exists among them a myriad of distinctions in shade. Some leaves are a dark olive green, some a light pastel green; others again are a green colour in between. In fact the distinctions in shade are so numerous that it is unlikely that we will find two leaves sufficiently indistinguishable that we would choose to say that they are the same in any strict sense of the word.¹