 Discussions of time, space, identity and change have been part of philosophy since its earliest days, and not every question about persistence obviously concerns temporal parts. For example, can we give criteria of identity through time for artefacts, animals or people? What happens to a ship if you replace all of its planks one by one? What if you keep the old planks, then build a new ship out of them? In addressing these questions during recent decades, however, it has proven useful to discuss whether objects have temporal parts, because the answers that philosophers give to these questions can often depend upon whether they believe in temporal parts.