 It should also be noted that four dimensionalism differs from Chisholm's invocation of loose and popular identity in, at least, the following way. The persistence of an object for any length of time will, on a four dimensionalist view, require the existence of shorter lived objects setting aside the possibility of extended simples. The persistence for any length of time, on Chisholm's view, of a three dimensional object does not require the existence of shorter lived three dimensional objects. It does not do so because the object persisting for a lengthy period may undergo no change of parts.