Nirvana means extinction — first of all, the extinction of all concepts and notions. Our concepts about things prevent us from really touching them. We have to destroy our notions if we want to touch the real rose. When we ask, “Dear Buddha, are you a human being?” it means we have a concept about what a human being is. So the Buddha just smiles at us. It is his way of encouraging us to transcend our concepts and touch the real being that he is. A real being is quite different from a concept.