In his TED talk, ‘Queerer than we can suppose’, Richard Dawkins suggests that we may be more like waves than physical objects. He describes a crescent-shaped sand dune in Africa that moves about 17 metres each year. The grains of sand that make up the dune are constantly changing—being added to or removed from the dune by the wind. But the dune, as it moves, keeps its shape. He also points out that not a single atom in our bodies was there when we were children. We are, by analogy, like the sand dune: just as the dune consists of grains of sand that are continually changing, so we consist of atoms that are continually changing. Both we and the dune, it seems, are more like waves than objects.

Another analogy: We can take a box full of Lego blocks, choose a few of them, and build a model house. We can then replace individual blocks, one at a time, with similar blocks still left in the box. Eventually all the original blocks would be replaced, but the house would retain its original shape and appearance. Or perhaps the house’s appearance would change slightly: red blocks where before there were blue ones, for example. Is this a better analogy to describe us and our bodies? Are we an arrangement of atoms, and is it that particular arrangement that is “us”?

One more analogy: A song—or musical composition of any sort—may be passed along through time and space, perhaps for hundreds of years, and all around the world. It may be performed by any number of singers or musicians. And yet it remains the same song. Is this a useful analogy for how we remain the same person even though our bodies change constantly as we move through time and space?