Our world apparently existed as a worm or a caterpillar: it is now like a chrysalis. In its last revolution it will appear as a butterfly.
                                                    Charles Bonnet, Paligénésie philosophique, 1753

Time, experience, fire and water, habit, travel, the seasons, conception and death, dreams, perspectives, emotions transform us. Made of corruptible matter, we grow old and decline, and whatever expectations we may have of an invariable immortality are denied by memory and usage which also transform what they remember and use. The old metaphors that we have employed throughout the ages to define ourselves are all images of change: the coursing river, the falling leaves, the moulded clay, the ashes. Our identity stands always between the person we no longer are and the person we may one day become, never quite inhabiting the present and never quite inhabiting any other time. As soon as we say I am we define something that lies outside us, like the skin of a snake, another image of transformation. Verbal tricks allow us the illusion of constancy but merely illustrate the unfulfilled wish of constantly being. We tend to think of the past as the source of our existence; Miguel de Unamuno thought that time flowed from the future into the past, and back again. We exist in both currents, swept back through our many ghosts and forward to our future identities. Perhaps the emblem of all such metamorphoses is the Möbius strip, the one-sided strip that, like Unamuno's ...