Which risks does distance decorrelate?
The case for becoming multiplanetary rests on one claim: risks that are independent across worlds become perfectly correlated when everything is in one place.1
Some risks do decorrelate with distance: asteroids, supervolcanoes, most pandemics. Others travel with the settlers: a hostile optimizing system, a self-propagating ideology, a shared supply chain.2
Any redundancy argument that does not separate the two has not been made yet. That split is the question I ask of every space thesis before I back it.