<P> Colloquially, "das Gleiche" and "dasselbe" are used somewhat interchangeably . </P> <P> Ted Sider and others have proposed that considering objects to extend across time as four - dimensional causal series of three - dimensional "time - slices" could solve the ship of Theseus problem because, in taking such an approach, all four dimensional objects remain numerically identical to themselves while allowing individual time - slices to differ from each other . The aforementioned river, therefore, comprises different three - dimensional time - slices of itself while remaining numerically identical to itself across time; one can never step into the same river - time - slice twice, but one can step into the same (four - dimensional) river twice . </P>

Each part gets its meaning from the body as a whole