"[T]he human necessity is not just to know, but also to cherish and protect the things that are known, and to know the things that can only be known by cherishing. If we are to protect the world's multitude of places and creatures, then we must know them, not just conceptually but imaginatively as well. They must be pictured in the mind and in memory; they must be known with affection, 'by heart,' so that in seeing or remembering them the heart may be said to 'sing,' to make music peculiar to its recognition of each particular place or creature that it knows well. . . . To know imaginatively is to know intimately, particularly, precisely, gratefully, reverently, and with affection."