ABSTRACT
Nevertheless, it may still seem that the river is identical with a volume of water like wSATURDAY at a particular time. Now, if you bathe in the river at one location and then at another, you bathe in the same river by bathing in different spatial parts of it. On another conception currently popular among philosophers the river is a sequence of temporal parts, or time-slices; it has four dimensions, three spatial, and one temporal. On this view, if you bathed in the river on successive days, you would be bathing in the same river by bathing in different temporal parts of it, just as you can bathe in the same river by bathing in different spatial parts of it. The different temporal parts could be identified with different, but related, volumes of water. However, the fourdimensional view has a problem too. The river is something which changes, and change seems to require a persistent substance which changes. If we merely had a sequence of temporal parts, a sequence of related volumes of water, what would change?
