Thanks for this helpful lecture. I had a question regarding David's discussion on dynamical sufficiency. He mentions that "every single level is necessary and sufficient to predict its own future". I understand the argument on sufficiency (and he goes into this in quite a bit of detail), but I'm not sure I follow regarding the necessity. Are we saying that we can not predict the system's future by looking at the level below, but have to look at the emergent level? Wouldn't this imply that there is some inconsistency between both levels, ie something is "added" to the system at the higher level that does not exist at the level below and therefore predictions at the lower level will be wrong? Or are we saying prediction is simply not possible at the lower level (perhaps because of computational complexity given the multiple variables)? Thanks a lot in advance!