"A tree is like a sculpture; it occupies space in aesthetically interesting ways. But in traditional sculpture, there is always a discernible difference between the raw material and the form that has been purposefully imposed on that material. With a real tree, there is no such distinction. God may have made the tree, but he did not make it out of some nontree substance the way a sculptor can make the image of a human being out of a nonhuman material like clay or marble "