  Even in the case of the similarity of my pain now to my pain ten minutes ago, there will be unimportant dissimilarities, and also between my pain and your pain. Compare topiary, making use of an analogy exploited by Quine in a different connection. In English country gardens the tops of box hedges are often cut in various shapes, for example peacock shapes. One might make generalizations about peacock shapes on box hedges, and one might say that all the imitation peacocks on a particular hedge have the same shape. However if we approach the two imitation peacocks and peer into them to note the precise shapes of the twigs that make them up we will find differences. Whether we say that two things are similar or not is a matter of abstractness of description. If we were to go to the limit of concreteness the types would shrink to single membered types, but there would still be no ontological difference between identity theory and functionalism.