 What moral should we draw from this communication breakdown? Some perdurantists think ‘so much the worse for endurantists: they can’t even say what they’re against’. Some endurantists think ‘so much the worse for perdurantists: their theory doesn’t even make sense’. And some philosophers on both sides look for a neutral way to spell out the notion of a temporal part (for more detail on this, see the reading suggestions at the end of this section). For now, let’s take it that the basic idea of a temporal part is well-enough understood, perhaps via the analogy with spatial parts; later sections will show how the idea is put to work.