 The other doctrine which usually goes along with perdurantism is Humean Supervenience. This is the claim that, roughly speaking, facts about which intrinsic properties are instantiated at which points determine all the facts there are. There are no irreducibly holistic facts. In conjunction with perdurantism, this entails that all the facts about a given persisting object supervene upon intrinsic facts about its briefest temporal parts. That’s to say, if you fix what’s happening at each moment, you’ve fixed everything. This sounds pretty plausible, but it turns out that it’s rather difficult to reduce facts about motion, for example, to suitable moment-by-moment facts.